IAB node dual connectivity setup method and communication apparatus

ABSTRACT

The present disclosure relates to integrated access and backhaul (IAB) node dual connectivity setup methods and communication apparatus. In one example method, a first IAB node sets up a first F1 interface with a primary donor node of the first IAB node. The first IAB node obtains an internet protocol (IP) address anchored at a secondary donor node connected to the first IAB node and/or configuration information of a serving cell, of the first IAB node, belonging to the secondary donor node. The first IAB node sends, to the secondary donor node, a request for setting up a second F1 interface with the secondary donor node, where the request includes the configuration information of the serving cell, of the first IAB node, belonging to the secondary donor node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2019/116874, filed on Nov. 8, 2019, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

This application relates to the communication field, and morespecifically, to an IAB node dual connectivity setup method and acommunication apparatus.

BACKGROUND

In an integrated access and backhaul (IAB) network, an IAB node mayprovide a wireless access service and a wireless backhaul service foruser equipment. Service data of the user equipment is sent by the IABnode to an IAB donor node through a wireless backhaul link. The IABdonor node may also be referred to as a donor IAB node, an IAB donorbase station, or a donor base station. The IAB donor node is connectedto a 5G core network element through an NG interface.

Currently, once the IAB node is deployed, the IAB node does not move,and mobility of the IAB node is not considered. With networkdevelopment, a mobile network scenario is one of important scenarios of5G. Because the IAB node can provide wireless backhaul, the IAB node issuitable for improving network coverage and capacities in the mobilescenario. Therefore, the IAB node may alternatively be deployed on amobile device (for example, a car, a high-speed railway, or a subway),and moves as the mobile device moves.

In a process in which the IAB node moves, an IAB donor node connected tothe IAB node changes. Currently, in a process in which the IAB node ishanded over to the IAB donor node, not only the IAB node is handed overto a target IAB donor node, but also a child node of the IAB node needsto be handover to the target IAB donor node. Therefore, before handover,the IAB node needs to first send, to the child node of the IAB node,information configured by the target IAB donor node for the child nodeof the IAB node. In this case, a long handover latency is generated, andthe long handover latency causes a problem of service interruption.Consequently, communication quality is severely affected, andcommunication efficiency is reduced.

SUMMARY

This application provides an IAB node dual connectivity setup method anda communication apparatus, to reduce a latency for setting up an F1interface with a secondary donor node after an IAB node is handed overto the secondary donor node, avoid a problem of service interruptioncaused by a latency existing when the IAB node is hand over to a donornode, ensure communication quality, and improve communicationefficiency.

According to a first aspect, an IAB node dual connectivity setup methodis provided. The method may be performed by an IAB node, an IAB-DU ofthe IAB node, or a chip used in the IAB node or the IAB-DU. For example,the method is performed by the IAB node. The method includes: A firstIAB node sets up a first F1 interface with a primary donor node of thefirst IAB node. The first IAB node obtains an internes protocol IPaddress anchored at a secondary donor node connected to the first IABnode and/or configuration information of a serving cell, of the firstIAB node, belonging to the secondary donor node. The first IAB nodesends, to the secondary donor node, a request for setting up a second F1interface with the secondary donor node, where the request includes theconfiguration information of the serving cell, of the first IAB node,belonging to the secondary donor node. The IAB node may include a mobileterminal MT unit and a distributed unit DU, the primary donor node mayinclude a primary donor CU and a primary donor DU, and the secondarydonor node may include a secondary donor CU and a secondary donor DU.

According to the IAB node dual connectivity setup method provided in thefirst aspect, one IAB node sets up F1 interfaces with both a primarydonor CU and a secondary donor CU. Before the IAB node is handed overfrom the primary donor CU to the secondary donor CU, because the IAB-DUhas set up the F1 interface with the secondary donor CU in advance,after the IAB-DU is handed over to the secondary donor CU, F1 interfacesetup may not be triggered again. In this way, a latency for setting upthe F1 interface between the IAB-DU and the secondary donor CU after theIAB node is handed over to the secondary donor CU is reduced, and aproblem of service interruption caused by a latency existing when theIAB node is handed over to a donor node is avoided, thereby ensuringcommunication quality and improving communication efficiency.

In a possible implementation of the first aspect, the method furtherincludes: The first IAB node sends first indication information to thesecondary donor node, where the first indication information is used toindicate, to the secondary donor node, whether to start an operation ofactivating the serving cell, of the first IAB node, belonging to thesecondary donor node. In this implementation, a latency when the IABnode is handed over to a donor CU can be reduced, and the problem ofservice interruption caused by the latency existing when the IAB node ishanded over to a donor node is avoided, thereby ensuring communicationquality.

Optionally, before the IAB node is handed over to the secondary donorCU, the first indication information is used to indicate the secondarydonor node not to start the operation of activating the serving cell ofthe first IAB node.

Optionally, after the IAB node is handed over to the secondary donor CU,the first indication information is used to indicate the secondary donornode to start the operation of activating the serving cell of the firstIAB node.

In a possible implementation of the first aspect, the method furtherincludes: The first IAB node sends second indication information to thesecondary donor node, where the second indication information includesan identifier of the serving cell that the first IAB node requests thesecondary donor node to activate. In this implementation, the IAB-DUsends the second indication information to the secondary donor CU, andwhen the secondary donor CU starts an operation of activating servingcells, serving cells that need to be activated may be determined. Inthis way, normal communication in the serving cells that need to beactivated and communication between the serving cells that need to beactivated and the secondary donor node are ensured, thereby ensuringcommunication quality and avoiding service interruption caused by donornode handover.

In a possible implementation of the first aspect, the method furtherincludes: The first IAB node sends first information to the secondarydonor node, where the first information is used to request to allocatean IP address to the first IAB node. The first IAB node receives secondinformation from the secondary donor node, where the second informationincludes at least one of an IP address allocated to the first IAB node,an IP address prefix allocated to the first IAB node, or first n bits ofthe IP address allocated to the first IAB node, where n is an integergreater than 0. In this implementation, after a donor DU to which theIAB node is attached changes, the IAB node may request a donor CU towhich the IAB node is attached to allocate more IP addresses to the IABnode, to satisfy a requirement of communication between the IAB node andnew donor nodes (for example, the donor CU and the donor DU). This canensure normal communication between the IAB node and a target donornode, and ensure communication efficiency.

In a possible implementation of the first aspect, the first informationincludes at least one of a quantity of IP addresses requested to beallocated to the first IAB node, a length of the one or more IP addressprefixes requested to be allocated to the first IAB node, or a value ofn of first n bits of the IP address requested to be allocated to thefirst IAB node. In this implementation, the quantity of IP addressesrequested to be allocated to the first IAB node is explicitly orimplicitly indicated, so that flexibility of allocating the IP addressesto the first IAB node can be improved, and efficiency of allocating theIP addresses to the first IAB node can be improved.

In a possible implementation of the first aspect, a centralized unit CUof the secondary donor node includes a centralized unit-control planeCU-CP entity and a centralized unit-user plane CU-UP entity. The firstinformation further includes at least one of a quantity of IP addressesrequested to be allocated to an F1-C interface, a length of the one ormore IP address prefixes requested to be allocated to the F1-Cinterface, a value of x of first x bits of the IP address requested tobe allocated to the F1-C interface, a quantity of IP addresses requestedto be allocated to an F1-U interface, a length of the one or more IPaddress prefixes requested to be allocated to the F1-U interface, or avalue of y of first y bits of the IP address requested to be allocatedto the F1-U interface, where the F1-C interface is a communicationinterface between the first IAB node and the CU-CP entity of thesecondary donor node, the F1-U interface is a communication interfacebetween the first IAB node and the CU-UP entity of the secondary donornode, and both x and y are integers greater than 0. In thisimplementation, a quantity of IP addresses that are requested to beallocated to the first IAB node and that are used for F1-C interfacecommunication and F1-U interface communication is explicitly orimplicitly indicated, so that flexibility of allocating the IP addressesto the first IAB node can be improved, and efficiency of allocating theIP addresses to the first IAB node can be improved. In addition, in anarchitecture in which a control plane and a user plane of the secondarydonor CU are split, efficiency and quality of communication between thefirst IAB node and the CU-CP entity and between the first IAB node andthe CU-UP entity are ensured.

In a possible implementation of the first aspect, the method furtherincludes: The first IAB node receives third indication information fromthe secondary donor node, where the third indication information is usedto indicate at least one of a first IP address used for the F1-Uinterface in the one or more IP addresses allocated to the first IABnode, a first IP address prefix used for the F1-U interface, first ybits of the first IP address used for the F1-U interface, a second IPaddress used for the F1-C interface in the one or more IP addressesallocated to the first IAB node, a second IP address prefix for the F1-Cinterface, or first x bits of the second IP address used for the F1-Cinterface. In this implementation, the first IAB node clearly knows theIP address used for F1-C interface communication and the IP address usedfor F1-U interface communication, so that in an architecture in which acontrol plane and a user plane of the secondary donor CU are split,efficiency and quality of communication between the first IAB node andthe CU-CP entity and between the first IAB node and the CU-UP entity areensured.

In a possible implementation of the first aspect, the secondary donornode includes a centralized unit CU and at least one distributed unitDU. The method further includes: The first IAB node receives fourthindication information from the secondary donor node, where the fourthindication information is used to indicate information that is about theDU of the secondary donor node and that corresponds to the IP addressallocated to the first IAB node.

According to a second aspect, an IAB node dual connectivity setup methodis provided. The method may be performed by a secondary donor node of afirst IAB node, a centralized unit CU (secondary donor CU) of thesecondary donor node of the first IAB node, or a chip used in thesecondary donor node or the secondary donor CU. An IAB node may includea mobile terminal MT unit and a distributed unit DU, a primary donornode may include a primary donor CU and a primary donor DU, and thesecondary donor node may include the secondary donor CU and a secondarydonor DU. For example, the method is performed by the secondary donornode. The method includes: The secondary donor node receives, from afirst IAB node, a request for setting up a second F1 interface with thesecondary donor node, where the secondary donor node is a secondarydonor node of the first IAB node. The secondary donor node sends, to thefirst IAB node, a response for setting up the second F1 interface, wherethe response includes information about the secondary donor node. Whenthe secondary donor node sets up the second F1 interface with the firstIAB node, the first IAB node maintains a first F1 interface with aprimary donor node of the first IAB node.

According to the IAB node dual connectivity setup method provided in thesecond aspect, one IAB node (one IAB-DU) sets up F1 interfaces with botha primary donor CU and a secondary donor CU. Before the IAB node ishanded over from the primary donor CU to the secondary donor CU, becausethe IAB-DU has set up the F1 interface with the secondary donor CU inadvance, after the IAB-DU is handed over to the secondary donor CU, F1interface setup may not be triggered again. In this way, a latency forsetting up the F1 interface between the IAB-DU and the secondary donorCU after the IAB node is handed over to the secondary donor CU isreduced, and a problem of service interruption caused by a latencyexisting when the IAB node is handed over to a donor node is avoided,thereby ensuring communication quality and improving communicationefficiency.

In a possible implementation of the second aspect, the method furtherincludes: The secondary donor node receives first indication informationfrom the first IAB node, where the first indication information is usedto indicate, to the secondary donor node, whether to start an operationof activating a serving cell, of the first IAB node, belonging to thesecondary donor node.

Optionally, before the IAB node is handed over to the secondary donorCU, the first indication information is used to indicate the secondarydonor node not to start the operation of activating the serving cell ofthe first IAB node.

Optionally, after the IAB node is handed over to the secondary donor CU,the first indication information is used to indicate the secondary donornode to start the operation of activating the serving cell of the firstIAB node.

In a possible implementation of the second aspect, the method furtherincludes: The secondary donor node receives second indicationinformation from the first IAB node, where the second indicationinformation includes an identifier of the serving cell that the firstIAB node requests the secondary donor node to activate. In thisimplementation, the IAB-DU sends the second indication information tothe secondary donor CU, and when the secondary donor CU starts anoperation of activating serving cells, serving cells that need to beactivated may be determined. In this way, normal communication in theserving cells that need to be activated and communication between theserving cells that need to be activated and the secondary donor node areensured, thereby ensuring communication quality and avoiding serviceinterruption caused by donor node handover.

In a possible implementation of the second aspect, the method furtherincludes: The secondary donor node receives first information from thefirst IAB node, where the first information is used to request toallocate an IP address to the first IAB node. The secondary donor nodesends second information to the first IAB node, where the secondinformation includes at least one of an IP address allocated to thefirst IAB node, an IP address prefix allocated to the first IAB node, orfirst n bits of the IP address allocated to the first IAB node, where nis an integer greater than 0.

In a possible implementation of the second aspect, the first informationincludes at least one of a quantity of IP addresses requested to beallocated to the first IAB node, a length of the one or more IP addressprefixes requested to be allocated to the first IAB node, or a value ofn of first n bits of the IP address requested to be allocated to thefirst IAB node. In this implementation, the quantity of IP addressesrequested to be allocated to the first IAB node is explicitly orimplicitly indicated, so that flexibility of allocating the IP addressesto the first IAB node can be improved, and efficiency of allocating theIP addresses to the first IAB node can be improved.

In a possible implementation of the second aspect, a centralized unit CUof the secondary donor node includes a centralized unit-control planeCU-CP entity and a centralized unit-user plane CU-UP entity. The firstinformation further includes at least one of a quantity of IP addressesrequested to be allocated to an F1-C interface, a length of the one ormore IP address prefixes requested to be allocated to the F1-Cinterface, a value of x of first x bits of the IP address requested tobe allocated to the F1-C interface, a quantity of IP addresses requestedto be allocated to an F1-U interface, a length of the one or more IPaddress prefixes requested to be allocated to the F1-U interface, or avalue of y of first y bits of the IP address requested to be allocatedto the F1-U interface, where the F1-C interface is a communicationinterface between the first IAB node and the CU-CP entity of thesecondary donor node, the F1-U interface is a communication interfacebetween the first IAB node and the CU-UP entity of the secondary donornode, and both x and y are integers greater than 0. In thisimplementation, a quantity of IP addresses that are requested to beallocated to the first IAB node and that are used for F1-C interfacecommunication and F1-U interface communication is explicitly orimplicitly indicated, so that flexibility of allocating the IP addressesto the first IAB node can be improved, and efficiency of allocating theIP addresses to the first IAB node can be improved. In addition, in anarchitecture in which a control plane and a user plane of the secondarydonor CU are split, efficiency and quality of communication between thefirst IAB node and the CU-CP entity and between the first IAB node andthe CU-UP entity are ensured.

In a possible implementation of the second aspect, the method furtherincludes: The secondary donor node sends third indication information tothe first IAB node, where the third indication information is used toindicate at least one of a first IP address used for the F1-U interfacein the one or more IP addresses allocated to the first IAB node, a firstIP address prefix used for the F1-U interface, first y bits of the firstIP address used for the F1-U interface, a second IP address used for theF1-C interface in the one or more IP addresses allocated to the firstIAB node, a second IP address prefix used for the F1-C interface, orfirst x bits of the second IP address used for the F1-C interface.

In a possible implementation of the second aspect, the secondary donornode includes a centralized unit CU and at least one distributed unitDU. The method further includes: The secondary donor node sends fourthindication information to the first IAB node, where the fourthindication information is used to indicate information that is about theDU of the secondary donor node and that corresponds to the IP addressallocated to the first IAB node.

In a possible implementation of the second aspect, the secondary donornode includes a centralized unit CU and a distributed unit DU. Themethod further includes: The CU of the secondary donor node sends thefirst information to the DU of the secondary donor node. The CU of thesecondary donor node receives, from the DU of the secondary donor node,at least one of the IP address allocated to the first IAB node, the IPaddress prefix allocated to the first IAB node, or the first n bits ofthe IP address allocated to the first IAB node.

In a possible implementation of the second aspect, the method furtherincludes: The secondary donor node receives a secondary station additionrequest message from the primary donor node, where the secondary stationaddition request message is used to request to add the secondary donornode as a secondary station of the first IAB node, and the secondarystation addition request message includes at least one of indicationinformation indicating that the first IAB node is a mobile IAB node, anidentifier of a first IAB node group, member information of the firstIAB node group, or topology information of the first IAB node group,where the first IAB node group is a group including the first IAB nodeand a child node of the first IAB node. In this implementation, a dualconnectivity procedure is introduced before IAB node handover. In aprocess in which the IAB node adds a secondary station, a primary IABdonor sends information about an IAB node group to a secondary IABdonor, and sets up a user plane backhaul link between the IAB node andthe secondary IAB donor in advance. When donor node handover isperformed subsequently, only an identifier of the IAB node group needsto be notified to the secondary IAB donor in a handover request, toreduce a handover processing latency in a subsequent handover process.

In a possible implementation of the second aspect, the method includes:The secondary donor node sends a secondary station addition responsemessage to the primary donor node, where the secondary station additionresponse message includes at least one of an IP address, of the firstIAB node, anchored at the secondary donor node or an IP address of thesecondary donor node.

In a possible implementation of the second aspect, the memberinformation of the first IAB node group includes at least one of anidentifier of the child node of the first IAB node, quality of serviceQoS information of a service of the child node of the first IAB node, orQoS information corresponding to a backhaul radio link control channelof the first IAB node under a topology of the primary donor node.

According to a third aspect, a method for adding a secondary station byan IAB node is provided. The method may be performed by a primary donornode of a first IAB node, a centralized unit CU (primary donor CU) ofthe primary donor node of the first IAB node, or a chip used in theprimary donor node or the primary donor CU. The IAB node may include amobile terminal MT unit and a distributed unit DU, the primary donornode may include the primary donor CU and a primary donor DU, and asecondary donor node may include a secondary donor CU and a secondarydonor DU. For example, the method is performed by the primary donornode. The method includes: The primary donor node sends a secondarystation addition request message to a first donor node, where thesecondary station addition request message is used to request to add thefirst donor node as a secondary donor node of a first IAB node, and theprimary donor node is a primary donor node of the first IAB node. Thesecondary station addition request message includes at least one ofindication information indicating that the first IAB node is a mobileIAB node, an identifier of a first IAB node group, member information ofthe first IAB node group, or topology information of the first IAB nodegroup, where the first IAB node group is a group including the first IABnode and a child node of the first IAB node. The primary donor nodereceives a secondary station addition response message from the firstdonor node. The primary donor node sends seventh indication informationto the first IAB node, where the seventh indication information is usedto indicate the first IAB node to add the first donor node as thesecondary donor node.

According to the method for adding a secondary station by an IAB nodeprovided in the third aspect, a dual connectivity procedure isintroduced before IAB node handover. In a process in which the IAB nodeadds a secondary station, a primary IAB donor sends information about anIAB node group to a first IAB donor, and sets up a user plane backhaullink between the IAB node and the first IAB donor. When donor nodehandover is performed subsequently, only an identifier of the IAB nodegroup needs to be notified to the first donor node in a handoverrequest, to reduce a handover processing latency in a subsequenthandover process.

In a possible implementation of the third aspect, the member informationof the first IAB node group includes at least one of an identifier ofthe child node of the first IAB node, quality of service QoS informationof a service of the child node of the first IAB node, or QoS informationcorresponding to a backhaul radio link control channel of the first IABnode under a topology of the primary donor node.

In a possible implementation of the third aspect, the secondary stationaddition response message of the first donor node includes at least oneof an IP address, of the first IAB node, anchored at the first donornode or an IP address of the first donor node.

In a possible implementation of the third aspect, the method furtherincludes: The primary donor node sends a handover request message to thefirst donor node, where the handover request message includes theidentifier of the first IAB node group. The primary donor node receivesa handover response message from the first donor node, where thehandover response message is used to indicate the first IAB node to behanded over to the first donor node. In this implementation, a primaryIAB donor has sent information about an IAB node group to a first IABdonor, and sets up a user plane backhaul link between the IAB node andthe first IAB donor. Therefore, when donor node handover is performed,only an identifier of the IAB node group needs to be notified to thefirst donor node in a handover request, to reduce a handover processinglatency in a subsequent handover process.

In a possible implementation of the third aspect, the method furtherincludes: The primary donor node sends, to the first IAB node, an IPaddress, of the first IAB node, anchored at the first donor node and/orconfiguration information of a serving cell, of the first IAB node,belonging to the first donor node.

According to a fourth aspect, a method for reporting support of an IABfunction is provided, where the method is applied to an IABcommunication network. The IAB communication network includes an IABdonor node, and the IAB donor node includes a centralized unit CU and atleast one distributed unit DU. The CU includes a centralizedunit-control plane CU-CP entity and a centralized unit-user plane CU-UPentity. The method includes: The CU-UP entity of the donor nodegenerates fifth indication information, where the fifth indicationinformation is used to indicate that the CU-UP entity of the donor nodesupports an IAB function or supports access of an IAB node. The CU-UPentity of the donor node sends the fifth indication information to theCU-CP entity of the donor node.

According to the method for reporting support of an IAB functionprovided in the fourth aspect. When selecting CU-UP entities of thedonor node to perform data transmission, the CU-CP entity of the donornode can accurately select CU-UP entities that are of the donor node andthat support IAB, and use the CU-UP entities of the donor node toperform routing and bearer mapping before sending data, so as to ensurenormal user-plane transmission and ensure quality and efficiency of datatransmission of a terminal device.

Optionally, if a CU-UP entity of the donor node supports attaching orcan attach a DSCP/flow label to data of the terminal device, the CU-UPentity of the donor node supports the IAB function or supports access ofthe IAB node.

In a possible implementation of the fourth aspect, the fifth indicationinformation performs indication based on each public land mobile networkPLMN. In this implementation, flexibility of indicating that the CU-UPentity supports the IAB function or supports access of the IAB node canbe improved, and signaling overheads can be reduced.

In a possible implementation of the fourth aspect, that the CU-UP entityof the donor node sends the fifth indication information to the CU-CPentity of the donor node includes: The CU-UP entity of the donor nodesends an E1 interface setup request to the CU-CP entity of the donornode, where the E1 interface setup request includes the fifth indicationinformation, and an E1 interface is an interface between the CU-UPentity of the donor node and the CU-CP entity of the donor node. In thisimplementation, the CU-UP entity of the donor node actively triggers E1interface setup, and carries, in an E1 interface setup request message,indication information indicating that the CU-UP entity of the donornode supports the IAB function, supports access of the IAB node, orsupports IAB, to help the CU-CP entity of the donor node select anappropriate CU-UP entity of the donor node, and improve resourceutilization.

In a possible implementation of the fourth aspect, the method furtherincludes: The CU-UP entity of the donor node receives the E1 interfacesetup request from the CU-CP entity of the donor node, where the E1interface is an interface between the CU-UP entity of the donor node andthe CU-CP entity of the donor node. That the CU-UP entity of the donornode sends the fifth indication information to the CU-CP entity of thedonor node includes: The CU-UP entity of the donor node sends an E1interface setup response to the CU-CP entity of the donor node, wherethe E1 interface setup response includes the fifth indicationinformation. In this implementation, resource utilization can beimproved.

In a possible implementation of the fourth aspect, the method furtherincludes: The CU-UP entity of the donor node receives sixth indicationinformation from the CU-CP entity of the donor node, where the sixthindication information is used to indicate the CU-UP entity of the donornode to report a capability that the CU-UP entity of the donor nodesupports the IAB function or access of the IAB node.

According to a fifth aspect, a method for obtaining an IP address of anIAB node is provided. The method may be performed by a donor node of afirst IAB node, a centralized unit CU of the donor node of the first IABnode, or a chip used in the donor node or the donor CU. The first IABnode may include a mobile terminal MT unit and a distributed unit DU,and the donor node may include the donor CU and a donor DU. For example,the method is performed by the donor node. The method includes: Thedonor node receives first information from a first IAB node, where thefirst information is used to request to allocate one or more IPaddresses to the first IAB node. The donor node sends second informationto the first IAB node, where the second information includes the one ormore IP addresses allocated to the first IAB node, one or more IPaddress prefixes allocated to the first IAB node, or first n bits of theIP address allocated to the first IAB node, where n is an integergreater than 0.

According to the method for obtaining an IP address of an IAB nodeprovided in the fifth aspect, when the IAB node needs to obtain more IPaddresses, the IAB node may request a donor CU to which the IAB node isattached to allocate more IP addresses to the IAB node, to satisfy arequirement of communication between the IAB node and new donor nodes(for example, a donor CU and a donor DU). This can ensure normalcommunication between the IAB node and a target donor node, and ensurecommunication efficiency.

In a possible implementation of the fifth aspect, the first informationincludes at least one of a quantity of IP addresses requested to beallocated to the first IAB node, a length of the one or more IP addressprefixes requested to be allocated to the first IAB node, or a value ofn of first n bits of the IP address requested to be allocated to thefirst IAB node.

In a possible implementation of the fifth aspect, a centralized unit CUof the donor node includes a centralized unit-control plane CU-CP entityand a centralized unit-user plane CU-UP entity. The first informationfurther includes at least one of a quantity of IP addresses requested tobe allocated to an F1-C interface, a length of the one or more IPaddress prefixes requested to be allocated to the F1-C interface, avalue of x of first x bits of the IP address requested to be allocatedto the F1-C interface, a quantity of IP addresses requested to beallocated to an F1-U interface, a length of the one or more IP addressprefixes requested to be allocated to the F1-U interface, or a value ofy of first y bits of the IP address requested to be allocated to theF1-U interface, where the F1-C interface is a communication interfacebetween the first IAB node and the CU-CP entity of the donor node, theF1-U interface is a communication interface between the first IAB nodeand the CU-UP entity of the donor node, and both x and y are integersgreater than 0.

In a possible implementation of the fifth aspect, the method furtherincludes: The donor node sends third indication information to the firstIAB node, where the third indication information is used to indicate atleast one of a first IP address used for the F1-U interface in the oneor more IP addresses allocated to the first IAB node, a first IP addressprefix used for the F1-U interface, first y bits of the first IP addressused for the F1-U interface, a second IP address used for the F1-Cinterface in the one or more IP addresses allocated to the first IABnode, a second IP address prefix used for the F1-C interface, or first xbits of the second IP address used for the F1-C interface.

In a possible implementation of the fifth aspect, the donor nodeincludes a centralized unit CU and at least one distributed unit DU. Themethod further includes: The donor node sends fourth indicationinformation to the first IAB node, where the fourth indicationinformation is used to indicate information that is about the DU of thedonor node and that corresponds to the one or more IP addressesallocated to the first IAB node.

In a possible implementation of the fifth aspect, the donor nodeincludes a centralized unit CU and a distributed unit DU. The methodfurther includes: The CU of the donor node sends the first informationto the DU of the donor node.

The CU of the donor node receives, from the DU of the donor node, atleast one of the one or more IP addresses allocated to the first IABnode, the one or more IP address prefixes allocated to the first IABnode, or the first n bits of the IP address allocated to the first IABnode.

According to a sixth aspect, a communication apparatus is provided. Theapparatus includes units configured to perform the steps in any one ofthe first aspect or the possible implementations of the first aspect.

According to a seventh aspect, a communication apparatus is provided.The apparatus includes units configured to perform the steps in any oneof the second aspect and the third aspect or the possibleimplementations of the second aspect and the third aspect, or theapparatus includes units configured to perform the steps in any one ofthe fifth aspect or the possible implementations of the fifth aspect.

According to an eighth aspect, a communication apparatus is provided.The apparatus includes units configured to perform the steps in any oneof the fourth aspect or the possible implementations of the fourthaspect.

According to a ninth aspect, a communication apparatus is provided. Theapparatus includes at least one processor and a memory, and the at leastone processor is configured to perform the method in any one of thefirst aspect or the possible implementations of the first aspect.

According to a tenth aspect, a communication apparatus is provided. Theapparatus includes at least one processor and a memory, and the at leastone processor is configured to perform the method in any one of thesecond aspect or the possible implementations of the second aspect, theat least one processor is configured to perform the method in any one ofthe third aspect or the possible implementations of the third aspect, orthe at least one processor is configured to perform the method in anyone of the fifth aspect or the possible implementations of the fifthaspect.

According to an eleventh aspect, a communication apparatus is provided.The apparatus includes at least one processor and a memory, and the atleast one processor is configured to perform the method in any one ofthe fourth aspect or the possible implementations of the fourth aspect.

According to a twelfth aspect, a communication apparatus is provided.The apparatus includes at least one processor and an interface circuit,and the at least one processor is configured to perform the method inany one of the first aspect or the possible implementations of the firstaspect.

According to a thirteenth aspect, a communication apparatus is provided.The apparatus includes at least one processor and an interface circuit,and the at least one processor is configured to perform the method inany one of the second aspect or the possible implementations of thesecond aspect, the at least one processor is configured to perform themethod in any one of the third aspect or the possible implementations ofthe third aspect, or the at least one processor is configured to performthe method in any one of the fifth aspect or the possibleimplementations of the fifth aspect.

According to a fourteenth aspect, a communication apparatus is provided.The apparatus includes at least one processor and an interface circuit,and the at least one processor is configured to perform the method inany one of the fifth aspect or the possible implementations of the fifthaspect.

According to a fifteenth aspect, an IAB node is provided. The IAB nodeincludes the communication apparatus provided in the sixth aspect, theIAB node includes the communication apparatus provided in the ninthaspect, or the IAB node includes the communication apparatus provided inthe twelfth aspect.

According to a sixteenth aspect, an IAB donor node is provided. The IABdonor node includes the communication apparatus provided in the seventhaspect, the IAB donor node includes the communication apparatus providedin the tenth aspect, or the IAB donor node includes the communicationapparatus provided in the thirteenth aspect.

According to a seventeenth aspect, a CU-CP entity of a donor node isprovided. The CU-CP entity of the donor node includes the communicationapparatus provided in the eighth aspect, the CU-CP entity of the donornode includes the communication apparatus provided in the eleventhaspect, or the CU-CP entity of the donor node includes the communicationapparatus provided in the fourteenth aspect.

According to an eighteenth aspect, a computer program product isprovided. The computer program product includes a computer program, andwhen the computer program is executed by a processor, the computerprogram is configured to perform the method in any one of the firstaspect to the fifth aspect or the possible implementations of the firstaspect to the fifth aspect.

According to a nineteenth aspect, a computer-readable storage medium isprovided. The computer-readable storage medium stores a computerprogram, and when the computer program is executed, the computer programis configured to perform the method in any one of the first aspect tothe fifth aspect or the possible implementations of the first aspect tothe fifth aspect.

According to a twentieth aspect, a communication system is provided. Thecommunication system includes the foregoing IAB node and IAB donor node.

According to a twenty-first aspect, a chip is provided. The chipincludes a processor, configured to invoke a computer program from amemory and run the computer program, so that a communication device onwhich the chip is installed performs the method in any one of the firstaspect to the fifth aspect or the possible implementations of the firstaspect to the fifth aspect, or performs the method in any one of thesecond aspect or the possible implementations of the second aspect.

According to an IAB node dual connectivity setup method in embodimentsof this application, one IAB node sets up F1 interfaces with both aprimary donor CU and a secondary donor CU. Before the IAB node is handedover from the primary donor CU to the secondary donor CU, because theIAB-DU has set up the F1 interface with the secondary donor CU inadvance, after the IAB-DU is handed over to the secondary donor CU, F1interface setup may not be triggered again. In this way, a latency forsetting up the F1 interface between the IAB-DU and the secondary donorCU after the IAB node is handed over to the secondary donor CU isreduced, and a problem of service interruption caused by a latencyexisting when the IAB node is handed over to a donor node is avoided,thereby ensuring communication quality and improving communicationefficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a gNB using a CU-DU split structure;

FIG. 2 is a schematic diagram of an architecture in which a gNB-CU-CPand a gNB-CU-UP are split;

FIG. 3 is a schematic diagram of data transmission performed by aterminal device through two-hop data backhaul (BH);

FIG. 4 is a schematic diagram of a control plane protocol stack duringtwo-hop data backhaul;

FIG. 5 is a schematic diagram of a user plane protocol stack duringtwo-hop data backhaul;

FIG. 6 is a schematic diagram of a communication system applicable to anembodiment of this application;

FIG. 7 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to an embodiment of thisapplication;

FIG. 8 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to another embodiment of thisapplication;

FIG. 9 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to another embodiment of thisapplication;

FIG. 10 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to still another embodiment of thisapplication;

FIG. 11 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to still another embodiment of thisapplication;

FIG. 12 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to still another embodiment of thisapplication;

FIG. 13 is a schematic interaction diagram of an IAB node dualconnectivity setup method according to still another embodiment of thisapplication;

FIG. 14 is a schematic diagram of an application scenario of a methodfor reporting support of an IAB function according to an embodiment ofthis application;

FIG. 15 is a schematic interaction diagram of a method for reportingsupport of an IAB function according to an embodiment of thisapplication;

FIG. 16 is a schematic diagram of a supported PLMN list according to anembodiment of this application;

FIG. 17 is a schematic interaction diagram of a method for reportingsupport of an IAB function according to another embodiment of thisapplication;

FIG. 18 is a schematic interaction diagram of a method for reportingsupport of an IAB function according to another embodiment of thisapplication;

FIG. 19 is a schematic interaction diagram of a method for reportingsupport of an IAB function according to another embodiment of thisapplication;

FIG. 20 is a schematic flowchart of a method for adding a secondarystation by an IAB node according to an embodiment of this application;

FIG. 21 is a schematic flowchart of a method for obtaining an IP addressof an IAB node according to an embodiment of this application;

FIG. 22 is a schematic block diagram of a communication apparatusaccording to an embodiment of this application;

FIG. 23 is a schematic block diagram of another communication apparatusaccording to an embodiment of this application;

FIG. 24 is a schematic block diagram of still another communicationapparatus according to an embodiment of this application;

FIG. 25 is a schematic block diagram of another communication apparatusaccording to an embodiment of this application;

FIG. 26 is a schematic block diagram of another communication apparatusaccording to an embodiment of this application;

FIG. 27 is a schematic block diagram of still another communicationapparatus according to an embodiment of this application; and

FIG. 28 is a schematic diagram of a structure of an IAB node or an IABdonor node according to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions in this application withreference to the accompanying drawings.

The technical solutions in embodiments of this application may beapplied to various communication systems, such as a global system formobile communications (GSM), a code division multiple access (CDMA)system, a wideband code division multiple access (WCDMA) system, ageneral packet radio service (GPRS), a long term evolution (LTE) system,an LTE frequency division duplex (FDD) system, an LTE time divisionduplex (TDD) system, a universal mobile telecommunications system(UMTS), a worldwide interoperability for microwave access (WiMAX)communication system, a future 5th generation (5G) system, or a newradio (NR) system.

A terminal device in embodiments of this application may be userequipment, an access terminal, a subscriber unit, a subscriber station,a mobile station, a remote station, a remote terminal, a mobile device,a user terminal, a terminal, a wireless communication device, a useragent, or a user apparatus. The terminal device may alternatively be acellular phone, a cordless phone, a session initiation protocol (SIP)phone, a wireless local loop (WLL) station, a personal digital assistant(PDA), a handheld device having a wireless communication function, acomputing device, another processing device connected to a wirelessmodem, a vehicle-mounted device, a wearable device, a terminal device inthe future 5G network, a terminal device in a future evolved public landmobile communication network (PLMN), or the like. This is not limited inembodiments of this application.

A network device in embodiments of this application may be a deviceconfigured to communicate with the terminal device. The network devicemay be a base transceiver station (BTS) in the global system for mobilecommunications (GSM) system or the code division multiple access (CDMA)system, a NodeB (NB) in the wideband code division multiple access(WCDMA) system, an evolved NodeB (eNB or eNodeB) in the LTE system, anew radio NodeB (gNB), or a radio controller in a cloud radio accessnetwork (CRAN) scenario. Alternatively, the network device may be arelay node, an access point, a vehicle-mounted device, a wearabledevice, a network device in the future 5G network, a network device inthe future evolved PLMN network, or the like. This is not limited inembodiments of this application.

In embodiments of this application, the terminal device or the networkdevice includes a hardware layer, an operating system layer runningabove the hardware layer, and an application layer running above theoperating system layer. The hardware layer includes hardware such as acentral processing unit (CPU), a memory management unit (MMU), and amemory (also referred to as a main memory). The operating system may beany one or more computer operating systems, for example, a Linuxoperating system, a Unix operating system, an Android operating system,an iOS operating system, or a Windows operating system, that implementservice processing by using a process. The application layer includesapplications such as a browser, an address book, word processingsoftware, and instant messaging software. In addition, a specificstructure of an execution body of a method provided in embodiments ofthis application is not specifically limited in embodiments of thisapplication, provided that a program that records code of the methodprovided in embodiments of this application can be run to performcommunication according to the method provided in embodiments of thisapplication. For example, the method provided in embodiments of thisapplication may be performed by the terminal device or the networkdevice, or a function module that can invoke and execute the program inthe terminal device or the network device.

In addition, aspects or features of this application may be implementedas a method, an apparatus, or a product that uses standard programmingand/or engineering technologies. The term “product” used in thisapplication covers a computer program that can be accessed from anycomputer-readable component, carrier or medium. For example, acomputer-readable medium may include but is not limited to: a magneticstorage component (for example, a hard disk, a floppy disk, or amagnetic tape), an optical disc (for example, a compact disc (CD) or adigital versatile disc (DVD)), a smart card and a flash memory component(for example, an erasable programmable read-only memory (EPROM), a card,a stick, or a key drive). In addition, various storage media describedin this specification may indicate one or more devices and/or othermachine-readable media that are configured to store information. Theterm “machine-readable media” may include but is not limited to awireless channel, and various other media that can store, include,and/or carry instructions and/or data.

In an NR technology, an access network device (for example, a gNB) mayinclude one gNB centralized unit (CU) and one or more gNB distributedunits (DUs). The gNB-CU and the gNB-DU are different logical nodes, andmay be deployed on different physical devices or deployed on a samephysical device.

A CU-DU split structure used by the gNB is shown in FIG. 1 . The gNB-CUis connected to the gNB-DU through an F1 interface, the gNB-CU isconnected to a 5G core network through an NG interface, and gNBs areconnected to each other through an Xn interface. The Xn interfaceincludes an Xn-C interface and an Xn-U interface. The Xn-C interface isused to transmit control plane signaling between the two gNBs, and theXn-U interface is used to transmit user plane data between the two gNBs.An interface between the gNB and UE is referred to as a Uu interface(namely, an interface between the UE and the gNB-DU). The terminaldevice accesses the gNB-CU through the gNB-DU. A peer physical (PHY)layer/media access control (MAC) layer/radio link control (RLC) layer ofthe terminal device is located on the gNB-DU, and a peer packet dataconvergence protocol (PDCP) layer/radio resource control (RRC)layer/service data adaptation protocol (SDAP) layer of the terminaldevice is located on the gNB-CU.

It should be understood that, the foregoing deployment of the protocollayers on the gNB-DU and the gNB-CU is merely one possibility, and theprotocol layers may be deployed in another manner. For example, the peerPHY layer/MAC layer of the terminal device is located on the gNB-DU, thepeer PDCP layer/RRC layer/SDAP layer of the terminal device is locatedon the gNB-CU, and the peer RLC layer of the terminal device is alsolocated on the gNB-CU. All these fall within the protection scope ofthis application, and are not limited herein in this application.

For a control plane, in an uplink (UL) direction, the gNB-DUencapsulates, into an F1 application protocol (F1AP) message of the F1interface, an RRC message generated by the terminal device, and sendsthe F1AP message to the gNB-CU. In a downlink (DL) direction, the gNB-CUencapsulates the RRC message into the F1 AP message and sends the F1APmessage to the gNB-DU. The gNB-DU extracts the RRC message from the FLAPmessage, maps the RRC message to a signaling radio bearer (SRB)corresponding to the Uu interface, and sends the signaling radio bearerto the terminal device.

For a user plane, in a UL direction, the gNB-DU maps, to a correspondinggeneral packet radio service tunneling protocol (GTP) tunnel, a datapacket that is of the terminal device and that is received from a dataradio bearer (DRB) of the Uu interface, and sends the GTP tunnel to thegNB-CU. In a DL direction, the gNB-CU maps the data packet of theterminal device to the corresponding GTP tunnel and sends the GTP tunnelto the gNB-DU. The gNB-DU extracts the data packet of the terminaldevice from the GTP tunnel, maps the data packet to the DRBcorresponding to the Uu interface, and sends the DRB to the terminaldevice.

If an architecture in which the control plane and the user plane aresplit is considered, the gNB-CU may be further divided into acentralized unit-control plane (CU-CP) entity (or may be referred to asa CU-CP node) and a centralized unit-user plane (CU-UP) entity (or maybe referred to as a CU-UP node). The gNB-CU-CP is a control planeentity, and is configured to provide signaling control. The gNB-CU-UP isa user plane entity, and is configured to provide transmission of dataof the terminal device. The gNB-CU-CP is connected to the gNB-CU-UPthrough an E1 interface, the gNB-CU-CP is connected to the gNB-DUthrough an F1-C interface, and the gNB-CU-UP is connected to the gNB-DUthrough an F1-U interface. A structure is shown in FIG. 2 .

FIG. 2 shows an architecture in which the gNB-CU-CP and the gNB-CU-UPare split. The gNB-CU-CP includes an RRC function and a PDCP controlplane function (for example, configured to process data on a signalingradio bearer). The gNB-CU-UP mainly includes an SDAP function and a PDCPuser plane function (for example, configured to process data on a radiobearer of the user equipment/an IAB node).

In the architecture shown in FIG. 2 , the following characteristics arefurther included:

-   -   one gNB includes one gNB-CU-CP, a plurality of gNB-CU-UPs, and a        plurality of gNB-DUs;    -   one DU can be connected only to one gNB-CU-CP;    -   one CU-UP can be connected only to one gNB-CU-CP;    -   one DU can be connected to a plurality of gNB-CU-UPs under        control of a same CU-CP; and    -   one CU-UP can be connected to a plurality of gNB-DUs under        control of a same CU-CP.

It should be understood that, FIG. 2 is only an example and should notimpose any limitation on the gNB architecture. For example, in anarchitecture in which a CU and a DU are split and a CP and a UP aresplit, the gNB may include only one gNB-CU-UP, one gNB-CU-CP, and onegNB-DU, or may include more gNB-CU-UPs and gNB-DUs. This is not limitedherein in this application.

A 5G communication system imposes stricter requirements on variousnetwork performance indicators in an all-round manner. For example, acapacity indicator is increased by 1000 times, wider coverage isrequired, and ultra-high reliability and an ultra-low latency arerequired. Therefore, an integrated access and backhaul (IAB) technologyis introduced.

In an IAB network, a relay node (RN), or may be referred to as an IABnode, may provide a wireless access service and a wireless backhaulservice for the user equipment. Specifically, service data of the userequipment is transmitted by the IAB node to an IAB donor node through awireless backhaul link. The IAB donor node may also be referred to as adonor IAB node or an IAB donor base station. In an NR system, the IABdonor base station may be a donor gNodeB (DgNB). In an LTE system (orreferred to as a 4G system), the IAB donor base station may be a donoreNodeB (DeNB). Certainly, the IAB donor node may alternatively bereferred to as a gNB, an eNB, or an IAB donor for short.

The IAB donor may alternatively use a CU-DU split architecture. To bespecific, the IAB donor includes an IAB donor CU (or may be referred toas a donor CU) and an IAB donor DU (or may be referred to as a donorDU). An interface between the IAB donor CU and the IAB donor DU is an F1interface. The IAB node may include a mobile terminal (MT) unit and adistributed unit (DU). The IAB-MT may also be referred to as IAB-UE, hasa function of the terminal device, and mainly completes an operationsimilar to that of the terminal device. The IAB-DU has some functions ofa base station, and mainly completes an operation similar to that of thebase station.

For the IAB donor, the donor DU has a function similar to that of thegNB-DU in NR, and the donor CU has a function similar to that of thegNB-CU in NR.

For the IAB node, the IAB-DU has a function similar to that of thegNB-DU in NR, and provides an access service for a child node of theIAB-DU. The child node of the IAB-DU may be a terminal device, or may beanother IAB node. The IAB-MT is similar to the terminal device, and isconfigured to provide data backhaul. An IAB node accessed by theterminal device may be referred to as an access IAB node, and an IABnode on a path between the access IAB node and the IAB donor is referredto as an intermediate IAB node.

A two-hop data backhaul (BH) scenario is used as an example. As shown inFIG. 3 , a terminal device accesses an IAB node 2. In this case, the IABnode 2 is referred to as an access IAB node (or a previous-hop parentnode of the terminal device), and the terminal device is referred to asa next-hop child node of the IAB node 2. An IAB node 1 is referred to asan intermediate IAB node, in other words, a previous-hop parent node ofthe IAB node 1 is an IAB donor node, or a next-hop child node of the IABdonor is the IAB node 1. A next-hop child node of the IAB node 1 is theIAB node 2. A peer PHY layer, MAC layer, and RLC layer of the terminaldevice are located on the access IAB node (namely, on a DU of the IABnode 2), and a peer PDCP layer, SDAP layer, and RRC layer of theterminal device are located on a donor CU. An IAB node uses a layer 2(L2) data forwarding architecture. The following shows a specific userplane protocol stack and a specific control plane protocol stack:

FIG. 4 is a schematic diagram of a control plane protocol stack duringtwo-hop data backhaul. As shown in FIG. 4 , an access IAB node (namely,a DU of an IAB node 2) encapsulates, into an F1 AP message, an RRCmessage generated by a terminal device, and sends the F1 AP message to adonor CU. If the donor CU uses a CP-UP split architecture, the DU of theIAB node 2 encapsulates, into the F1AP message, the RRC messagegenerated by the terminal device and sends the FLAP message to a donorCU-CP. An interface between the DU of the IAB node 2 and the donor CU-CPis also referred to as an F1-C interface.

FIG. 5 is a schematic diagram of a user plane protocol stack duringtwo-hop data backhaul. As shown in FIG. 5 , a corresponding GTP tunnel(a GTP tunnel per UE bearer) is set up, for a service bearer of eachterminal device, between an access IAB node (namely, a DU of an IAB node2) and a donor CU. If the donor CU uses a CP-UP split architecture, theDU of the IAB node 2 sends a service of the terminal device to a donorCU-UP through the corresponding GTP tunnel. An interface between the DUof the IAB node 2 and the donor CU-UP is also referred to as an F1-Uinterface.

Currently, once an IAB node is deployed, the IAB node does not move, andmobility of the IAB node is not considered. With network development, amobile network scenario is one of important scenarios of 5G. Because theIAB node can provide wireless backhaul, the IAB node is suitable forimproving network coverage and capacities in the mobile scenario. In thescenario, because the IAB node is deployed on a mobile device (forexample, a high-speed railway, a car, or a subway) and moves with themobile device, the IAB node may be referred to as a mobile IAB node.

Regardless of a mobile IAB node or a fixed IAB node (namely, an IAB nodethat does not move), provided that an IAB donor node connected to theIAB node changes, the IAB node may be referred to as a handover IABnode. To reduce a problem of a signaling storm caused by the handoverIAB node in a handover process (when an IAB node is handed over, childnodes of the IAB node need to be handed over together with the IAB node,and a signaling storm is caused by independent handover procedurestriggered by the child nodes of the IAB node), the handover IAB node anda child node of the handover IAB node may be considered as a group. Thegroup may be referred to as an IAB node group or a handover IAB nodegroup. In other words, in the group, the handover IAB node may be usedas a head node, and the child node of the handover IAB node is handedover together with the head node. For example, when the handover IABnode is handed over to an IAB donor node, the child node of the handoverIAB node is handed over together with the handover IAB node. However, inthe handover process, a topology relationship between the handover IABnode and the child node of the handover IAB node remains unchanged.

Currently, in the handover process of the IAB node group, an IAB node(or may be referred to as a mobile IAB node) can communicate with onlyone previous-hop IAB donor node at any moment. An example in which anIAB node is handed over from a source donor node to a target donor nodeis used for description. The source donor node includes a source donorCU and a source donor DU, the target donor node includes a target donorCU and a target donor DU, and the IAB node includes an IAB-MT and anIAB-DU.

A main process in which the IAB node is handed over from the sourcedonor node to the target donor node includes:

The IAB node (specifically, the IAB-MT) and a child node (for example, aterminal device) of the IAB node are used as a group. In other words, ina handover preparation process, the source donor CU migrates contextinformation of the IAB node and context information of the child node ofthe IAB node to the target donor CU together.

Further, the target donor CU generates RRC configuration information forthe child node of the IAB node, where the RRC configuration informationincludes configuration information of a PDCP layer of the terminaldevice and a new security parameter (a security algorithm and/or aparameter for deriving a new air interface key by the terminal device)selected for transmitting data of the terminal device in an airinterface, and sends the RRC configuration information to the terminaldevice through the source donor CU.

The target donor CU generates handover command information for theIAB-MT, and indicates, through the source donor CU, the IAB-MT toexecute a handover process.

After the IAB-MT is handed over to the target donor CU, the IAB-DUtriggers setup of a stream control transmission protocol (SCTP)association with the target donor CU.

The IAB-DU triggers setup of an F1 interface with the target donor CU.

Corresponding GTP tunnels are set up between the IAB-DU and the targetdonor CU for different bearers of the terminal device. In this way, theIAB node can resume data transmission of the child node of the IAB node.

Although the foregoing solution can avoid the problem of the signalingstorm caused in the process in which the IAB node is handed over to adonor node, a latency when the child node of the IAB node resumes datatransmission is still long. Once a handover or re-setup procedure occurson the IAB node to which the IAB-DU belongs, a connected donor CUchanges. In this case, the IAB-DU needs to delete an F1 interfacebetween the IAB-DU and the source donor CU and re-set up an F1 interfacebetween the IAB-DU and the target donor CU. In other words, datatransmission can be resumed only after a new F1 interface is set upbetween the IAB-DU and the target donor CU and corresponding GTP tunnelsare set up for different bearers of the child node of the IAB node. Thisgenerates a long handover latency, and the long handover latency causesa problem of service interruption. Consequently, communication qualityis severely affected and communication efficiency is reduced.

In view of this, this application provides an IAB node dual connectivitysetup method. Before an IAB node is handed over to a donor node, a dualconnectivity procedure is introduced. To be specific, the IAB node isconnected to both a source donor node and a secondary donor node, and anF1 interface between the IAB node and the secondary donor node is set upfor the IAB node in advance. In this way, after the IAB node is handedover to the secondary donor node, there is no need to trigger aprocedure of setting up the F1 interface with the secondary donor node,to reduce a latency generated when the IAB node is handed over to thedonor node, ensure communication quality, and improve communicationefficiency.

For ease of understanding embodiments of this application, acommunication system applicable to embodiments of this application isfirst briefly described with reference to FIG. 6 .

FIG. 6 is a schematic diagram of a communication system applicable to anembodiment of this application. As shown in FIG. 6 , the mobilecommunication system 100 may include a mobile IAB node 110, a source IABdonor node 120, and a target IAB donor node 130. Child nodes of themobile IAB node 110 include a terminal device 111 and a terminal device112. First, the mobile IAB node is in coverage of the source IAB donornode, and accesses the source IAB donor node. Second, as the mobile IABnode moves, the mobile IAB node enters an overlapping area covered bythe source IAB donor node and the target IAB donor node. The mobile IABnode may start a dual connectivity operation, and access both the sourceIAB donor node and the target IAB donor node. In other words, the sourceIAB donor node is used as a primary IAB donor node, and the target IABdonor node is used as a secondary IAB donor node. Then, as the mobileIAB node moves, the mobile IAB node enters coverage of the target IABdonor node. In this case, the mobile IAB node executes a handoverprocess of handover from a dual-connectivity state in which the mobileIAB node is connected to both the source IAB donor node and the targetIAB donor node to a single-connectivity state in which the mobile IABnode is connected only to the target IAB donor node. In a process inwhich the mobile IAB node is handed over from the source IAB donor nodeto the target IAB donor node, the IAB node dual connectivity setupmethod provided in this application may be used to for donor nodehandover.

It should be noted that, for ease of understanding, FIG. 6 is merely aschematic diagram in which the mobile IAB node and the child nodes ofthe mobile IAB node that are included in the communication system 100 ishanded over from the source IAB donor node 120 to the target IAB donornode 130. However, this should not constitute any limitation on thisapplication. The communication system 100 may further include morenetwork nodes. For example, the child nodes of the mobile IAB node 110may further include more terminal devices and/or IAB nodes. The IABdonor node, the IAB node, and the terminal device that are included inthe communication system shown in FIG. 6 may be the IAB donor node, theIAB node, and the terminal device that are in the foregoing variousforms. These are not shown one by one in the figures in embodiments ofthis application.

It should be noted that, all embodiments of this application areapplicable to a mobile IAB scenario, and are also applicable to an IABnode handover scenario (a scenario in which an IAB node does not move,and handover occurs due to quality of an IAB node link).

The following describes in detail the IAB node dual connectivity setupmethod provided in this application with reference to FIG. 7 . FIG. 7 isa schematic flowchart of an IAB node dual connectivity setup method 200according to an embodiment of this application. The method 200 may beapplied to the scenario shown in FIG. 6 . Certainly, the method mayalternatively be applied to another scenario in which an IAB node needsto be handed over to a donor node. This is not limited herein in thisembodiment of this application.

It should be understood that, in the following descriptions, a method ineach embodiment is described by using an example in which the method ineach embodiment is performed by an IAB node and an IAB donor node. Byway of example but not limitation, the method may alternatively beperformed by chips used in the IAB node and the IAB donor node.

As shown in FIG. 7 , the method 200 shown in FIG. 7 may include stepS210 to step S250. The following describes in detail the steps in themethod 200 with reference to FIG. 3 . The method 200 includes thefollowing steps.

-   -   S210: A first IAB node sets up a first F1 interface with a        primary donor node of the first IAB node.    -   S220: The first IAB node obtains an internet protocol (IP)        address anchored at a secondary donor node connected to the        first IAB node and/or configuration information of a serving        cell, of the first IAB node, belonging to the secondary donor        node.    -   S230: The first IAB node sends, to the secondary donor node, a        request for setting up a second F1 interface with the secondary        donor node, where the request includes the configuration        information of the serving cell, of the first IAB node,        belonging to the secondary donor node. Correspondingly, the        secondary donor node receives the request.

Specifically, when the first IAB node sends, to the secondary donornode, the request for setting up the F1 interface with the secondarydonor node, the first IAB node maintains the first F1 interface with theprimary donor node.

-   -   S240: The secondary donor node sends response information to the        first IAB node in response to the request, where the response        information includes information about the secondary donor node.        Correspondingly, the first IAB node receives the response        information.

In this way, the first IAB node completes a process of setting up thesecond F1 interface with the secondary donor node. The second F1interface is used to transmit application layer information (forexample, an F1 AP message) between the first IAB node and the secondarydonor node.

Specifically, in this embodiment of this application, the first IAB nodemay be a mobile IAB node, and the first IAB node has set up a connectionto the primary donor node (or referred to as a source donor node) of thefirst IAB node and performs data transmission. The first IAB node mayinclude an IAB-MT and an IAB-DU, and the primary donor node (or may bereferred to as a primary IAB donor node) may include a primary donor CUand a primary donor DU. For the first IAB node, the source donor node isused as the primary donor node of the first IAB node. In other words, asource donor CU and a source donor DU are also referred to as theprimary donor CU and the primary donor DU. In other words, in S210, theIAB-MT of the first IAB node has been connected to the primary donor CU.For a control plane, the IAB-DU of the first IAB node has set up an F1interface (namely, the first F1 interface) with the primary donor CU,and the first F1 interface is used to transmit the application layerinformation (for example, the F1AP message) between the IAB-DU and theprimary donor CU. For a user plane, corresponding GTP tunnels have beenset up, for different bearers of a child node (for example, a terminaldevice) of the first IAB node, between the IAB-DU and the primary donorCU.

The IAB-MT of the first IAB node may add the secondary donor node as asecondary station of the IAB-MT by using a secondary station additionprocedure. The secondary donor node (or may be referred to as asecondary IAB donor node) may further include a secondary donor CU and asecondary donor DU. For the first IAB node, a target donor node is usedas the secondary donor node of the first IAB node. In other words, atarget donor CU and a target donor DU are also referred to as thesecondary donor CU and the secondary donor DU. In other words, theIAB-MT is connected to both the primary donor CU and the secondary donorCU, where the primary donor CU is used as a primary station, and thesecondary donor CU is used as a secondary station.

After the IAB-MT adds the secondary donor node as the secondary stationof the IAB-MT, in S220, the first IAB node obtains the IP addressanchored at the secondary donor node connected to the first IAB nodeand/or the configuration information of the serving cell, of the IAB-DU,belonging to the secondary donor node. Specifically, when the IAB-MT isconnected to the primary donor node, the IAB-MT obtains the IP addressto facilitate communication with the primary donor node, where the IPaddress and the primary donor node belong to a same network segment. Inaddition, the IAB-DU obtains the configuration information of theserving cell of the IAB-DU, where the configuration information of theserving cell is associated with the primary donor node. For example, anidentifier of the serving cell of the IAB-DU includes an identifier ofthe primary donor node. When the IAB-MT is connected to the secondarydonor node, the IAB-MT needs to obtain a new IP address, where the IPaddress and the secondary donor node belong to a same network segment,so that the IAB-MT can communicate with the secondary donor node. Inaddition, the IAB-DU needs to obtain configuration information of a newserving cell. In other words, the configuration information of theserving cell is associated with the secondary donor node. For example,an identifier of the serving cell of the IAB-DU includes an identifierof the secondary donor node.

It should be understood that, in this embodiment of this application,unless otherwise specified, each serving cell in this embodiment of thisapplication is a serving cell of the IAB-DU, but information, such as anidentifier, of the serving cell of the IAB-DU changes due to a change ofthe donor node.

In a possible implementation, the IAB-DU may request, from an operation,administration, and maintenance (OAM) server through the primary IABdonor node, to obtain the configuration information of the serving cell,of the IAB-DU, belonging to the secondary IAB donor node; or the IAB-DUrequests, from an OAM server through the secondary IAB donor node, toobtain the configuration information of the serving cell, of the IAB-DU,belonging to the secondary IAB donor node.

In a possible implementation, the IP address, of the IAB-DU, anchored atthe secondary IAB donor node may be allocated by the secondary donor CU,and sent to the primary IAB donor node by using a secondary nodeaddition request acknowledgment (S-Node Addition Request Acknowledge)message. The primary IAB donor node sends the IP address to the IAB-DU.Alternatively, the IP address, of the IAB-DU, anchored at the secondaryIAB donor node may be allocated by the secondary donor DU. The secondarydonor DU includes the allocated IP address in a context setup response(UE Context Setup Response) message of the terminal device and sends thecontext setup response message to the secondary donor CU. The secondarydonor CU sends the context setup response message to the primary IABdonor node by using an S-Node Addition Request Acknowledge message. Theprimary IAB donor node sends the IP address to the IAB-DU.Alternatively, the IP address, of the IAB-DU, anchored at the secondaryIAB donor node may be allocated by the OAM server, and sent to theIAB-DU through the primary IAB donor node or the secondary IAB donornode.

After the IAB-DU obtains the IP address anchored at the secondary donornode connected to the IAB-DU and/or the configuration information of theserving cell, of the IAB-DU, belonging to the secondary donor node, inS230, the first IAB node sends, to the secondary donor node, the requestfor setting up the second F1 interface with the secondary donor node,where the request includes the configuration information of the servingcell, of the first IAB node, belonging to the secondary donor node.Specifically, the IAB-DU of the first IAB node sends the request to thesecondary donor CU, where the request is used for setting up the secondF1 interface between the IAB-DU and the secondary donor CU. Optionally,the request may be an F1 interface setup request (F1 Setup Request)message or a newly defined FLAP message.

The request, sent by the IAB-DU, for setting up the second F1 interfacewith the secondary donor CU may include at least one of the followinginformation:

information about the IAB-DU, information about the serving cell of theIAB-DU, an RRC version that can be identified by the IAB-DU, orindication information indicating the secondary donor node not to startan operation of activating the serving cell of the IAB-DU.

The information about the IAB-DU may include an identifier (ID) of theIAB-DU and/or a name of the IAB-DU.

The information about the serving cell of the IAB-DU may include one ormore of a cell global identifier (CGI) of the serving cell, a physicalcell identifier (PCI) of the serving cell, a frequency of the servingcell, bandwidth of the serving cell, a public land mobile network (PLMN)of the serving cell, a system broadcast message MIB (Master InformationBlock) of the serving cell, a system broadcast message SIB 1 (SystemInformation Block 1) of the serving cell, or indication informationindicating that the serving cell has been activated.

In S240, after receiving the request sent by the IAB-DU, the secondarydonor CU may feed back, to the IAB-DU, a response to the request.Optionally, the response may be an F1 interface setup response (F1 SetupResponse) message or a newly defined F1 AP message. Optionally, theresponse may include information about the secondary donor CU, an RRCversion that can be identified by the secondary donor CU, and the like.The information about the secondary donor CU may include an identifierof the secondary donor CU, for example, a name of the secondary donorCU. Correspondingly, the IAB-DU receives the response information.

After the IAB-DU of the first IAB node receives the response, the firstIAB node completes the process of setting up the second F1 interfacewith the secondary donor node. The second F1 interface is used totransmit the application layer information between the IAB-DU and thesecondary donor CU. Although the IAB-DU sets up the second F1 interfacewith the secondary donor CU, the serving cell, of the IAB-DU, belongingto the secondary donor node is not activated. In other words, the IAB-DUdoes not broadcast, over an air interface, information such as the CGIabout a cell, of the IAB-DU, belonging to the secondary donor node.

The IAB-DU has set up an F1 interface with the primary donor CU, andthrough the foregoing steps S220 to S240, the IAB-DU also sets up an F1interface with the secondary donor CU, that is, the IAB-DU sets up theF1 interfaces with both the two donor CUs.

According to the IAB node dual connectivity setup method provided inthis application, one IAB node (one IAB-DU) sets up F1 interfaces withboth a primary donor CU and a secondary donor CU. Before the IAB node ishanded over from the primary donor CU to the secondary donor CU, becausethe IAB-DU has set up the F1 interface with the secondary donor CU inadvance, after the IAB-DU is handed over to the secondary donor CU, F1interface setup may not be triggered again. In this way, a latency forsetting up the F1 interface between the IAB-DU and the secondary donorCU after the IAB node is handed over to the secondary donor CU isreduced, and a problem of service interruption caused by a latencyexisting when the IAB node is handed over to a donor node is avoided,thereby ensuring communication quality and improving communicationefficiency.

Optionally, in some possible implementations of this application, thefirst IAB node further sends first indication information to thesecondary donor node, where the first indication information is used toindicate the secondary donor node (secondary donor CU) not to start anoperation of activating the serving cell, of the first IAB node,belonging to the secondary donor node, or the first indicationinformation is used to indicate the secondary donor node (secondarydonor CU) to start the operation of activating the serving cell, of thefirst IAB node, belonging to the secondary donor node. The followingprovides descriptions separately.

FIG. 8 is a schematic flowchart of an IAB node dual connectivity setupmethod in some other embodiments of this application. The method 200further includes S231 based on the steps in the method shown in FIG. 7 .

-   -   S231: The first IAB node sends first indication information to        the secondary donor node, where the first indication information        is used to indicate the secondary donor node (secondary donor        CU) not to start an operation of activating the serving cell, of        the first IAB node, belonging to the secondary donor node.        Correspondingly, the secondary donor node receives the first        indication information.

For steps S210, S220, S230, and S240 shown in FIG. 8 , refer to theforegoing related descriptions of S210, S220, S230, and S240. Forbrevity, details are not described herein again.

Because the IAB-DU sets up the F1 interfaces with both the primary donorCU and the secondary donor CU, before the IAB-MT is handed over to thesecondary donor CU, the IAB-DU further communicates with the primarydonor CU. In other words, the IAB-DU still transmits the applicationlayer information through the first F1 interface between the primarydonor CU and the IAB-DU. The serving cell of the IAB-DU is a servingcell, of the IAB-DU, belonging to the primary donor node. In otherwords, although the IAB-DU sets up the F1 interface with the secondarydonor CU, the serving cell, of the IAB-DU, belonging to the secondarydonor node is not activated. Therefore, the IAB-DU does not broadcast,over an air interface, information such as the CGI about a cell, of theIAB-DU, belonging to the secondary donor node. Therefore, in S231, afterthe IAB-MT adds the secondary donor node as a secondary station andaccesses the secondary donor node, the IAB-DU of the first IAB node maysend the first indication information to the secondary donor CU of thesecondary donor node, where the first indication information is used toindicate the secondary donor CU not to start the operation of activatingthe serving cell, of the IAB-DU, belonging to the secondary donor CUconnected to the IAB-DU. Correspondingly, the secondary donor CUreceives the first indication information. After receiving the firstindication information, the secondary donor CU determines that theoperation of activating the serving cell of the IAB-DU does not need tobe started currently. In this case, the secondary donor CU does notsend, to the IAB-DU, indication information indicating the IAB-DU toactivate the serving cell.

Optionally, if in S240, the response, to the request, fed back by thesecondary donor CU to the IAB-DU does not carry an identifier of ato-be-activated serving cell, the IAB-DU considers that the servingcell, of the IAB-DU, belonging to the secondary donor node connected tothe IAB-DU is not activated.

According to the IAB node dual connectivity setup method provided inthis application, one IAB node (IAB-DU) sets up F1 interfaces with botha secondary donor node (secondary donor CU) and a primary donor node(primary donor CU). However, before the IAB node is handed over to thesecondary donor CU, a serving cell, of the IAB-DU, belonging to thesecondary donor node is not activated. According to the IAB node dualconnectivity setup method provided in this application, a latency whenthe IAB node is handed over to a donor CU can be reduced, and a problemof service interruption caused by a latency existing when the IAB nodeis handed over to a donor node is avoided, thereby ensuringcommunication quality.

It should be understood that, the first indication information may becarried in the request for setting up the second F1 interface with thedonor CU in S220 and sent to the secondary donor CU together. That is,the first indication information and the request for setting up thesecond F1 interface may be sent to the secondary donor CU in one pieceof signaling, or the first indication information and the request forsetting up the second F1 interface may be respectively sent to thesecondary donor CU in different signaling. This is not limited herein inthis embodiment of this application.

When a first IAB node working in a dual-connectivity mode needs to fallback to a single-connectivity mode, for example, when quality of a linkbetween the first IAB node and a primary IAB donor becomes worse, andquality of a link between the first IAB node and a secondary IAB donorbecomes better, the first IAB node may use the secondary IAB donor as aunique parent node (or access node). An IAB-MT in the first IAB node maytrigger a handover procedure, to be specific, the IAB-MT is handed overto the secondary IAB donor, and removes a connection to the primary IABdonor. After the IAB-MT is handed over to a secondary donor CU, anIAB-DU may notify the secondary IAB donor CU to activate the second F1interface that is set up in advance, and activate a serving cell, of theIAB-DU, belonging to the secondary IAB donor. FIG. 9 is a schematicflowchart of an IAB node dual connectivity setup method in some otherembodiments of this application. The method 200 further includes S232based on the steps in the method shown in FIG. 8 .

-   -   S232: The first IAB node (IAB-DU) sends first indication        information to the secondary donor node (secondary donor CU),        where the first indication information is used to indicate the        secondary donor node (secondary donor CU) to start an operation        of activating the serving cell, of the IAB-DU, belonging to the        secondary donor CU connected to the IAB-DU. Correspondingly, the        secondary donor node (secondary donor CU) receives the first        indication information.

For steps S210, S220, S230, S231, and S240 shown in FIG. 9 , refer tothe foregoing related descriptions of S210, S220, S230, S231, and S240.For brevity, details are not described herein again.

After the IAB-MT is handed over to the secondary IAB donor, and removesthe connection to the primary IAB donor, the IAB-MT is connected only tothe secondary donor CU. In S232, the IAB-DU in the first IAB node maysend the first indication information to the secondary donor CU. In thiscase, the first indication information is used to indicate the secondarydonor CU to start the operation of activating the serving cell, of theIAB-DU, belonging to the secondary donor CU, to be specific, request toactivate the second F1 interface that is set up in advance and activatethe serving cell, of the IAB-DU, belonging to the secondary donor CU.After receiving the first indication information, the secondary donor CUmay start the operation of activating the serving cell of the IAB-DU.Optionally, the secondary donor CU may send indication information tothe IAB-DU, where the indication information may be carried in anon-user equipment associated F1AP message (non-UE associated F1 APmessage) or a newly defined F1 AP message. The indication informationincludes information about a serving cell that the IAB-DU is requestedto activate. After receiving the indication information, the IAB-DU mayactivate the corresponding serving cell. In this way, after the firstIAB node is handed over to the secondary donor node, the first F1interface may be quickly activated, to reduce a latency caused byhandover and ensure that the first IAB node and a child node of thefirst IAB node can normally communicate with the secondary donor node,ensure communication quality, and avoid service interruption caused bythe handover latency.

It should be understood that, the indication information used toindicate the secondary donor CU not to start the operation of activatingthe serving cell, of the IAB-DU, belonging to the secondary donor nodeand the indication information used to indicate the secondary donor CUto start the operation of activating the serving cell may be carried insame signaling or different signaling and sent to the secondary donorCU. This is not limited herein in this application.

Optionally, in some possible implementations of this application, afterthe IAB-DU is handed over from the primary donor CU to the secondarydonor CU, a physical cell of the IAB-DU remains unchanged, but a name oran identifier of the physical cell changes. For example, assuming thatthere are four physical cells of the IAB-DU, when the IAB-DU isconnected to the primary donor CU, identifiers of the four physicalcells are 11, 12, 13, and 14 respectively. After the IAB-DU is handedover from the primary donor CU to the secondary donor CU, identifiers ofthe four physical cells change to 21, 22, 23, and 24 respectively. Cellswhose identifiers are 11 and 21 are a same physical cell, cells whoseidentifiers are 12 and 22 are a same physical cell, cells whoseidentifiers are 12 and 23 are a same physical cell, and cells whoseidentifiers are 14 and 24 are a same physical cell. The cell 21, thecell 22, the cell 23, and the cell 24 are serving cells, of the IAB-DU,belonging to the secondary donor node connected to the IAB-DU. When theIAB-DU is connected to the primary donor CU, only some cells may be inan active state. Therefore, after the IAB-DU is handed over to thesecondary donor CU, the IAB-DU needs to notify the secondary donor CU ofcells that need to be activated, and the cells that definitely need tobe activated may be cells that are already in the active state when theIAB-DU is connected to the primary donor CU, to provide reference forthe secondary donor CU to request to activate a cell of the IAB-DU.Specifically, FIG. 10 is a schematic flowchart of an IAB node dualconnectivity setup method in some other embodiments of this application.The method 200 further includes S233 based on the steps in the methodshown in FIG. 9 .

-   -   S233: The first IAB node sends second indication information to        the secondary donor node, where the second indication        information includes an identifier of the serving cell that the        first IAB node requests the secondary donor node to activate.

For steps S210, S220, S230, S231, S232, and S240 shown in FIG. 10 ,refer to the foregoing related descriptions of S210, S220, S230, S231,S232, and S240. For brevity, details are not described herein again.

In S233, the IAB-DU of the first IAB node may send the second indicationinformation to the secondary donor CU of the secondary donor node, wherethe second indication information includes the identifier of the servingcell that the IAB-DU requests the secondary donor CU to activate. Forexample, the identifier of the serving cell may include a CGI of theserving cell and/or a PCI of the serving cell. For differentiation, theserving cell that the IAB-DU requests the secondary donor CU to activateis referred to as a first cell, and the first cell may be a physicalcell that is already in the active state when the IAB-DU is connected tothe primary donor CU. The first cell may be some or all of serving cellsof the IAB-DU. The second indication information is used to indicate thesecondary donor CU node that the first cell needs to be activated.

For example, 1-bit indication information corresponding to an identifierof a serving cell may be used to indicate whether the serving cell needsto be activated. In a possible implementation, when the 1-bit indicationinformation is set to 0, it indicates that the serving cell needs to beactivated; or when the 1-bit indication information is set to 1, itindicates that the serving cell does not need to be activated. Inanother possible implementation, when the 1-bit indication informationis set to true, it indicates that the serving cell needs to beactivated; or when the 1-bit indication information does not occur, itindicates that the serving cell does not need to be activated.

The secondary donor CU receives the second indication information, anddetermines that the IAB-DU needs to activate at least the first cell.The secondary donor CU may send indication information to the IAB-DU,where the indication information may be carried in a non-UE associatedF1 AP message or a newly defined F1 AP message. The indicationinformation includes information about the first cell that the IAB-DU isrequested to activate. After receiving the indication information, theIAB-DU may activate the first cell.

It should be understood that, cells that the secondary donor CU requeststhe IAB-DU to activate may include only a to-be-activated cell, of theIAB-DU, belonging to the source IAB donor, that is, may include only thefirst cell. Certainly, in addition to the first cell, the cells that thesecondary donor CU requests the IAB-DU to activate may also includeother cells that the secondary donor CU expects the IAB-DU to activate(for example, more air interface resources on the secondary IAB donorare available, and more cells may be activated to provide services). Inother words, the first cell may be a subset of the cells that thesecondary donor CU requests the IAB-DU to activate.

It should be further understood that, the second indication informationmay alternatively be carried in the first indication information in S232and sent to the secondary donor CU together. In other words, the secondindication information and the first indication information in S232 maybe sent to the secondary donor CU in a same piece of signaling.Certainly, the second indication information and the first indicationinformation in S232 may alternatively be sent to the secondary donor CUin different signaling. This is not limited herein in this embodiment ofthis application.

It should be further understood that, when the IAB-DU is connected tothe primary donor CU, if all serving cells are in the active state, butterminal devices or IAB nodes are attached only to some of the servingcells, after the IAB-DU is handed over from the primary donor CU to thesecondary donor CU, the IAB-DU sends second indication information tothe secondary donor CU, where the indication information is used toindicate, to the secondary donor CU node, that only the serving cells towhich the terminal devices or the IAB nodes are attached need to beactivated. The secondary donor CU receives the second indicationinformation, and determines at least the serving cells, of the IAB-DU,that need to be activated. Whether another cell is activated depends onimplementation of the secondary donor CU.

The IAB-DU sends the second indication information to the secondarydonor CU, and when the secondary donor CU starts an operation ofactivating serving cells, serving cells that need to be activated may bedetermined. In this way, normal communication in the serving cells thatneed to be activated and communication between the serving cells thatneed to be activated and the secondary donor node are ensured, therebyensuring communication quality and avoiding service interruption causedby donor node handover.

Optionally, in some possible implementations of this application, thesecondary donor CU may further indicate the primary donor CU to releasethe first F1 interface between the primary donor CU and the IAB-DU. Forexample, the secondary donor CU may use an existing XnAP message or anewly defined XnAP message, where the message carries an identifier ofthe IAB-DU or a name of the IAB-DU, so that the primary donor CUreleases an F1 interface resource corresponding to the IAB-DU. Theexisting XnAP message may be an NG-RAN node Configuration Updatemessage, a UE Context Release message, or the like. This is not limitedherein in this embodiment of this application.

Optionally, in some other possible implementations of this application,FIG. 11 is a schematic flowchart of an IAB node dual connectivity setupmethod in some other embodiments of this application. The method 200further includes S250 and S251 based on the steps in the method shown inFIG. 7 .

-   -   S250: The first IAB node sends first information to the        secondary donor node, where the first information is used to        request to allocate an IP address to the first IAB node.    -   S251: The secondary donor node sends second information to the        first IAB node, where the second information includes at least        one of an IP address allocated to the first IAB node, an IP        address prefix allocated to the first IAB node, or first n bits        of the IP address allocated to the first IAB node, where n is an        integer greater than 0.

For steps S210, S220, S230, and S240 shown in FIG. 11 , refer to theforegoing related descriptions of S210, S220, S230, and S240. Forbrevity, details are not described herein again.

In S250, because a donor DU to which the first IAB node is attachedchanges, and the donor node is handed over from the primary donor DU tothe secondary donor DU, the first IAB node needs to re-obtain more IPaddresses, for example, set up the second F1 interface with thesecondary donor CU by using the IP address. In addition, in anothercase, for example, in an initial access process of the first IAB node,or when the first IAB node may determine, based on implementation of thefirst IAB node, to request more IP addresses (may request more IPaddresses based on an upper-layer service requirement of the IAB node),or during or after an RRC re-setup or handover process, the first IABnode needs to obtain more IP addresses. This solution is also applicableto these scenarios. Therefore, in S250, the first IAB node sends thefirst information to the secondary donor node, where the firstinformation is used to request to allocate the IP address to the firstIAB node. Specifically, the first IAB node may send the firstinformation to the secondary donor CU of the secondary donor node.Correspondingly, the secondary donor CU receives the first information.Alternatively, the first IAB node may send the first information to thesecondary donor CU of the secondary donor node through the primary donorCU of the primary donor node. Correspondingly, the secondary donor CUreceives the first information through the primary donor CU.

In S251, after the secondary donor CU receives the first information,the secondary donor CU may allocate a new IP address to the first IABnode, or the secondary donor CU may request another node to allocate anIP address to the first IAB node, where the another node may be asecondary donor DU, an OAM server, a dynamic host configuration protocol(DHCP) server, or the like. After allocating an IP address to the firstIAB node, the nodes may send the allocated IP address to the secondarydonor CU. The secondary donor CU may send second information to thefirst IAB node, where the second information includes the IP addressallocated by the secondary donor CU or the IP address allocated by theanother node to the first IAB node. Alternatively, the secondary donorCU may send the second information to the first IAB node through theprimary donor CU.

Optionally, the second information may include at least one of the oneor more IP addresses allocated to the first IAB node, the one or more IPaddress prefixes allocated to the first IAB node, or first n bits of theone or more IP address allocated to the first IAB node, where n is aninteger greater than 0. When the second information includes the IPaddress prefix allocated to the first IAB node, or the first n bits ofthe IP address allocated to the first IAB node, the first IAB node maydetermine a quantity of remaining bits other than a length of the one ormore IP address prefixes, or may determine a quantity of remaining bitsother than the first n bits of the IP address, to obtain a plurality ofavailable IP addresses of the IAB node. For example, assuming that atotal length of an IP address is 32 bits, if it is indicated that alength of the one or more IP address prefixes is 30 bits, the length ofthe IP address prefix allocated by the secondary donor CU or the anothernode to the first IAB node is 30 bits, and the first IAB node maydetermine the remaining two bits other than the 30-bit length of the IPaddress prefix. In other words, the first IAB node requests to allocatefour IP addresses, and correspondingly, the secondary donor CU or theanother node allocates four IP addresses to the first IAB node.

According to the IAB node dual connectivity setup method provided inthis application, after a donor DU to which an IAB node is attachedchanges, the IAB node may request a donor CU to which the IAB node isattached to allocate more IP addresses to the IAB node, to satisfy arequirement of communication between the IAB node and new donor nodes(for example, the donor CU and the donor DU). This can ensure normalcommunication between the IAB node and a target donor node, and ensurecommunication efficiency.

It should be understood that, the method shown in FIG. 8 to FIG. 10 mayalternatively include S250 and S251.

Optionally, in a possible implementation, the first information includesat least one of a quantity of IP addresses requested to be allocated tothe first IAB node, a length of the one or more IP address prefixesrequested to be allocated to the first IAB node, or a value of n offirst n bits of the IP address requested to be allocated to the firstIAB node.

Specifically, the first information may explicitly indicate the quantityof IP addresses requested to be allocated to the first IAB node, thatis, the first information includes the quantity of IP addressesrequested to be allocated to the first IAB node. Certainly, the firstinformation may alternatively implicitly indicate the quantity of IPaddresses requested to be allocated to the first IAB node. For example,the first information includes the length of the IP address prefixrequested to be allocated to the first IAB node, or includes the valueof n of the first n bits of the IP address requested to be allocated tothe first IAB node. In this way, the quantity of IP addresses requestedto be allocated to the first IAB node may be determined based on aquantity of remaining bits of the IP address. For example, assuming thata total length of an IP address is 64 bits, and the first informationincludes first 60 bits of the IP address requested to be allocated tothe first IAB node, the second information may include the first 60 bitsof the IP address allocated to the first IAB node, and the first IABnode may determine the remaining 4 bits other than the first 60 bits ofthe IP address, that is, it is implicitly indicated that 16 IP addressesare requested to be allocated to the first IAB node.

The quantity of IP addresses requested to be allocated to the first IABnode is explicitly or implicitly indicated, so that flexibility ofallocating the IP addresses to the first IAB node can be improved, andefficiency of allocating the IP addresses to the first IAB node can beimproved.

Optionally, in some possible implementations of this application, thesecondary donor CU may be further divided into a CU-CP entity (which mayalso be referred to as a CU-CP node) and at least one CU-UP entity(which may also be referred to as a CU-UP node). The CU-UP entity andthe CU-CP entity may be distributed on different physical devices, ormay be disposed on a same physical device. The CU-CP entity includes anRRC function and a PDCP control plane function (for example, configuredto process data on a signaling radio bearer). The CU-UP entity includesan SDAP function and a user plane function of a PDCP protocol stack (forexample, configured to process data on a radio bearer of the userequipment). An F1-C interface is a communication interface between thefirst IAB node and the CU-CP entity, and an F1-U interface is acommunication interface between the first IAB node and the CU-UP entity.

Therefore, the first information may further include at least one of aquantity of IP addresses requested to be allocated to the F1-Cinterface, a length of the one or more IP address prefixes requested tobe allocated to the F1-C interface, a value of x of first x bits of theIP address requested to be allocated to the F1-C interface, a quantityof IP addresses requested to be allocated to the F1-U interface, alength of the one or more IP address prefixes requested to be allocatedto the F1-U interface, or a value of y of first y bits of the IP addressrequested to be allocated to the F1-U interface. Both x and y areintegers greater than 0. It should be understood that, if the firstinformation includes the first n bits of the IP address requested to beallocated to the first IAB node, the quantity of IP addresses requestedto be allocated may be determined based on the remaining bits of the IPaddress, that is, the quantity of IP addresses requested to be allocatedto the first IAB node=2^((total quantity of bits of the IP address-n)).The quantity of IP addresses requested to be allocated needs to be equalto a sum of the quantity of IP addresses used for the F1-C interface andthe quantity of IP addresses used for the F1-U interface. If the firstinformation further includes the first x bits of the IP addressrequested to be allocated to the F1-C interface, the quantity of IPaddresses requested to be allocated to the F1-Cinterface=2^((total quantity of bits of the IP address-x)). Similarly,if the quantity of IP addresses requested to be allocated to the F1-Uinterface=2^((total quantity of bits of the IP address-y)),2^((total quantity of bits of the IP address-n))=2^((total quantity of bits of the IP address-x))+2^((total quantity of bits of the IP address-y)).Optionally, the quantity of IP addresses that the first IAB noderequests to allocate may alternatively be greater than the sum of thequantity of IP addresses used for the F1-C interface and the quantity ofIP addresses used for the F1-U interface. This is not limited herein inthis application.

When allocating IP addresses to the first IAB node, the secondary donorCU or the another node may clearly know the quantity of IP addressesthat need to be allocated to the F1-C interface and/or the quantity ofIP addresses that need to be allocated to the F1-U interface. Similarly,the quantity of IP addresses allocated to the F1-C interface may beindicated in an explicit or implicit manner, and the quantity of IPaddresses allocated to the F1-U interface may also be indicated in anexplicit or implicit manner. For example, if the first informationincludes the length of the IP address prefix requested to be allocatedto the F1-C interface, or the value of x of the first x bits of the IPaddress requested to be allocated to the F1-C interface, it may beconsidered that the first information implicitly indicates the quantityof IP addresses requested to be allocated to the F1-C interface. Aquantity of IP addresses that are requested to be allocated to the firstIAB node and that are used for F1-C interface communication and F1-Uinterface communication is explicitly or implicitly indicated, so thatflexibility of allocating the IP addresses to the first IAB node can beimproved, and efficiency of allocating the IP addresses to the first IABnode can be improved. In addition, in an architecture in which a controlplane and a user plane of the secondary donor CU are split, efficiencyand quality of communication between the first IAB node and the CU-CPentity and between the first IAB node and the CU-UP entity are ensured.

Optionally, the value of x and the value of y may be the same, or may bedifferent.

Optionally, in some possible implementations of this application, thedonor node may send third indication information to the first IAB node,where the third indication information is used to indicate at least oneof a first IP address used for the F1-U interface in the one or more IPaddresses allocated to the first IAB node, a first IP address prefixused for the F1-U interface, first y bits of the first IP address usedfor the F1-U interface, a second IP address used for the F1-C interfacein the one or more IP addresses allocated to the first IAB node, asecond IP address prefix used for the F1-C interface, or first x bits ofthe second IP address used for the F1-C interface.

Specifically, in S251, the secondary donor CU may send secondinformation to the first IAB node, where the second information includesat least one of the one or more IP addresses allocated to the first IABnode, an IP address prefix allocated to the first IAB node, or first nbits of the IP address allocated to the first IAB node. However, thesecondary donor CU may be further divided into a CU-CP entity and atleast one CU-UP entity, the F1-C interface is a communication interfacebetween the first IAB node and the CU-CP entity, and the F1-U interfaceis a communication interface between the first IAB node and the CU-UPentity. Therefore, the secondary donor CU may further send thirdindication information to the first IAB node, where the third indicationinformation is used to indicate IP addresses (namely, the first IPaddress) used for F1-U interface communication and/or IP addresses(namely, the second IP address) used for F1-C interface communication inthe plurality of IP addresses allocated to the first IAB node.Alternatively, the third indication information is used to indicate IPaddress prefixes, used for F1-U interface communication and/or IPaddress prefixes, used for F1-C interface communication in the pluralityof IP address prefixes allocated to the first IAB node. Alternatively,the third indication information is used to indicate bits, of IPaddresses, used for F1-U interface communication and/or bits, of IPaddresses, used for F1-C interface communication in first n bits of theplurality of IP addresses allocated to the first IAB node.

In a possible implementation, the secondary donor CU may further sendsecond information to the first IAB node, where the second informationincludes the one or more IP addresses allocated to the first IAB node.After receiving the one or more allocated IP addresses, the first IABnode determines IP addresses used for F1-C interface communicationand/or IP addresses used for F1-U interface communication.

In another possible implementation, if the OAM server allocates IPaddresses to the first IAB node, the OAM server may further indicate IPaddresses (namely, the first IP address) used for F1-U interfacecommunication and/or IP addresses (namely, the second IP address) usedfor F1-C interface communication in the plurality of IP addressesallocated to the first IAB node.

In this embodiment, the first IAB node clearly knows the IP address usedfor F1-C interface communication and the IP address used for F1-Uinterface communication, so that in an architecture in which a controlplane and a user plane of the secondary donor CU are split, efficiencyand quality of communication between the first IAB node and the CU-CPentity and between the first IAB node and the CU-UP entity are ensured.

It should be understood that, in this embodiment of this application,the third indication information may alternatively be carried in thesecond information in S251 and sent to the first IAB node together. Inother words, the third indication information and the second informationin S251 may be sent to the first IAB node in a same piece of signaling.Certainly, the third indication information and the second informationin S251 may alternatively be sent to the first IAB node in differentsignaling. This is not limited herein in this embodiment of thisapplication.

Optionally, in some possible implementations of this application,because the secondary donor node may be further divided into a secondarydonor CU and at least one secondary donor DU, the secondary donor CU mayfurther send fourth indication information to the first IAB node, wherethe fourth indication information is used to indicate information thatis about the secondary donor DU and that corresponds to the IP addressallocated to the first IAB node. The information about the secondarydonor DU may be an identifier of the secondary donor DU, a name of thesecondary donor DU, an address of a backhaul adaptation protocol layer(BAP) of the secondary donor DU, an IP address of the secondary donorDU, or the like.

It should be understood that, in this embodiment of this application,the fourth indication information may alternatively be carried in thesecond information in S251 or carried in the third indicationinformation and sent to the first IAB node together. In other words, thefourth indication information and the second information in S251 or thethird indication information may be sent to the first IAB node in a samepiece of signaling. Certainly, the fourth indication information, thesecond information in S251, and the third indication information mayalternatively be sent to the first IAB node in different signaling. Thisis not limited herein in this embodiment of this application.

Optionally, in some possible implementations of this application,because the secondary donor node may be further divided into a secondarydonor CU and a secondary donor DU, when the secondary donor DU allocatesan IP address to the first IAB node, the secondary donor CU may forward,to the secondary donor DU, the first information sent by the first IABnode, and the secondary donor DU allocates the IP address to the firstIAB node. The secondary donor DU may send the allocated IP address tothe secondary donor CU, and the secondary donor CU notifies the firstIAB node of the allocated IP address. Alternatively, the secondary donorDU may further send, to the secondary donor CU, at least one of an IPaddress prefix allocated to the first IAB node or first n bits of the IPaddress allocated to the first IAB node. Optionally, the secondary donorDU may further send the third indication information to the secondarydonor CU.

Optionally, in some other possible implementations of this application,FIG. 12 is a schematic flowchart of an IAB node dual connectivity setupmethod in some other embodiments of this application. The method 200further includes S260 based on the steps in the method shown in FIG. 7 .

-   -   S260: The primary donor node sends a secondary station addition        request message to the secondary donor node, where the secondary        station addition request message is used to request to add the        secondary donor node as a secondary station of the first IAB        node, and the secondary station addition request message        includes:

at least one of indication information indicating that the first IABnode is a mobile IAB node, an identifier of a first IAB node group,member information of the first IAB node group, or topology informationof the first IAB node group, where the first IAB node group is a groupincluding the first IAB node and a child node of the first IAB node.Correspondingly, the secondary donor node receives the secondary stationaddition request message.

For steps S210, S220, S230, S240, and S260 shown in FIG. 12 , refer tothe foregoing related descriptions of S210, S220, S230, S240, and S250.For brevity, details are not described herein again.

To support IAB node group handover and reduce a service interruptionlatency caused by the handover, a dual connectivity procedure may beintroduced before the IAB-MT of the first IAB node is handed over to adonor IAB donor, and a user plane backhaul link between the IAB-MT andthe secondary IAB donor is set up in advance (where the backhaul link isused to transmit a service of a child node of an IAB node). In otherwords, before S220, the IAB-MT may add the secondary donor node as asecondary station of the IAB-MT. That is, the primary IAB donor is usedas a primary station of the IAB-MT, and the secondary IAB donor is usedas a secondary station of the IAB-MT. Before and after handover of thefirst IAB node, a DRB set up between the terminal device and the IAB-DUof the first IAB node remains unchanged.

Before the primary donor CU sends the secondary station addition requestmessage to the secondary donor CU, the IAB-MT of the first IAB node mayreport a measurement result to the secondary donor CU through theprimary donor DU. The measurement result includes quality of a linkbetween the first IAB node and the secondary IAB donor, and the like.Based on the measurement result of the IAB-MT, for example, when themeasurement result indicates that the quality of the link between thefirst IAB node and the secondary IAB donor is good, the primary donor CUdetermines to add the target IAB donor as a secondary station of theIAB-MT.

In S260, the primary donor CU may send the secondary station additionrequest message to the secondary donor CU. Optionally, the secondarystation addition request message may be an S-Node Addition Requestmessage. The secondary station addition request message is used torequest to add the secondary donor node as a secondary station of thefirst IAB node, and the secondary station addition request messageincludes:

at least one of indication information indicating that the first IABnode is a mobile IAB node, an identifier of a first IAB node group,member information of the first IAB node group, or topology informationof the first IAB node group. The first IAB node group is a groupincluding the first IAB node and a child node of the first IAB node.

The identifier of the first IAB node group may be a group identifier(group ID) of the first IAB node group.

The member information of the first IAB node group may includeinformation about the IAB-MT and information about all child nodes (forexample, UE) of the IAB-MT. The information about the UE includescontext information of the UE, an identifier of the UE (for example, acell radio network temporary identifier (C-RNTI) or a CGI), quality ofservice (QoS) information of a service of the UE, and the like. Theinformation about the IAB-MT includes bearer QoS informationcorresponding to a backhaul radio resource control link (BH RLCchannel), set up by the IAB-MT, of a topology of the source IAB donor.Optionally, the member information of the first IAB node group mayfurther include information about the IAB-DU, for example, an identifierof the IAB-DU, a name of the IAB-DU, an RRC version supported by theIAB-DU, and configuration information of a serving cell, of the IAB-DU,belonging to the primary donor node.

After the secondary donor CU receives the secondary station additionrequest message, the secondary donor CU sends a context setup requestmessage of the child node (for example, the UE) of the IAB-MT to thesecondary donor DU for the secondary donor DU to set up a context of theIAB-MT. After the secondary donor DU receives the context setup requestmessage, the secondary donor DU sends a context setup response (UEContext Setup Response) message to the secondary donor CU.

After receiving the context setup response message, the secondary donorCU sends a secondary station addition response message to the primarydonor node (primary donor CU). In other words, the secondary donor nodesends the secondary station addition response message to the primarydonor node. Optionally, the secondary station addition response messagemay be an S-Node Addition Request Acknowledge message.

The secondary station addition response message includes at least one ofan IP address, of the first IAB node (specifically, the IAB-DU),anchored at the secondary donor node or an IP address of the secondarydonor node (specifically, the secondary donor CU).

Optionally, the secondary station addition response message may furtherinclude at least one of identifiers (for example, XnAP IDs) of the firstIAB node and the child node of the first IAB node on an Xn interface ora tunnel identifier allocated by the secondary donor CU to a bearer ofthe child node of the first IAB node. The Xn interface is acommunication interface between the primary donor node and the secondarydonor node. Optionally, the tunnel identifier allocated to the bearer ofthe child node of the first IAB node may include an IP address of atunnel and a GTP-tunnel endpoint identifier (Tunnel Endpoint ID, TEID).

Further, the primary donor CU sends an RRC reconfiguration message tothe IAB-MT, where the RRC reconfiguration message is used to indicatethe IAB-MT to use the secondary IAB donor as a secondary station, andtrigger initiation of a random access procedure to the secondary IABdonor.

After receiving the RRC reconfiguration message, the IAB-MT sends an RRCreconfiguration complete message to the primary donor CU. Afterreceiving the RRC reconfiguration complete message, the primary donor CUsends a secondary node configuration complete (S-Node ReconfigurationComplete) message to the secondary donor CU.

Afterwards, the IAB-MT triggers the random access (Random AccessChannel, RACH) procedure with the secondary IAB donor. After the RACHprocedure, the IAB-MT performs security protection by using a peersecurity key of the target donor CU. In addition, the IAB-DU furtherobtains the configuration information of the serving cell, of theIAB-DU, belonging to the secondary IAB donor.

For example, the IAB-DU may request, from the OAM server through theprimary IAB donor, to obtain the configuration information of theserving cell, of the IAB-DU, belonging to the secondary IAB donor.Alternatively, the LAB-DU requests, from the OAM server through thesecondary IAB donor, to obtain configuration information of a new cell,of the IAB-DU, belonging to the secondary IAB donor.

Further, the IAB-DU obtains information about the IP address, of theIAB-DU, anchored at the target IAB donor.

For the obtaining, by the IAB-DU, the configuration information of theserving cell, of the IAB-DU, belonging to the secondary IAB donor, andobtaining the information about the IP address of the IAB-DU, anchoredat the target IAB donor, refer to the foregoing related descriptions inS220. For brevity, details are not described herein again.

Then, the IAB-DU sets up an SCTP connection to the secondary donor CUand sets up, in advance, an F1 interface between the IAB-DU and thesecondary donor CU.

According to the foregoing procedure, a dual connectivity procedure maybe introduced before the IAB-MT of the first IAB node is handed over toa donor IAB donor, a user plane backhaul link between the IAB-DU and thesecondary IAB donor is set up in advance, and the IAB-MT may add thesecondary donor node as a secondary station of the IAB-MT. In otherwords, the IAB-MT is connected to both the primary donor CU and thesecondary donor CU, where the primary donor CU is used as a primarystation, and the secondary donor CU is used as a secondary station. Inaddition, the F1 interface between the IAB-DU and the secondary donor CUis set up in advance, that is, the IAB-DU sets up the F1 interfaces withboth the two donor CUs.

According to the IAB node dual connectivity setup method provided inthis application, a dual connectivity procedure is introduced before IABnode handover. In a process in which an IAB node adds a secondarystation, a primary IAB donor sends information about an IAB node groupto a secondary IAB donor, and sets up a user plane backhaul link betweenthe IAB node and the secondary IAB donor in advance. When donor nodehandover is performed subsequently, only an identifier of the IAB nodegroup needs to be notified to the secondary IAB donor in a handoverrequest, to reduce a handover processing latency in a subsequenthandover process.

It should be understood that, the method shown in FIG. 8 to FIG. 11 mayalternatively include S270.

Optionally, in some other possible implementations of this application,FIG. 13 is a schematic flowchart of an IAB node dual connectivity setupmethod in some other embodiments of this application. The method 200further includes S261 and S262 based on the steps in the method shown inFIG. 12 .

-   -   S261: The primary donor node sends a handover request message to        the secondary donor node, where the handover request message        includes the identifier of the first IAB node group.    -   S262: The secondary donor node sends a handover response message        to the primary donor node, where the handover response message        is used to indicate the first IAB node to be handed over to the        secondary donor node.

For steps S210, S220, S230, S240, and S260 shown in FIG. 13 , refer tothe foregoing related descriptions of S210, S220, S230, S240, and S260.For brevity, details are not described herein again.

When the quality of the link between the IAB-MT of the first IAB nodeand the primary IAB donor becomes worse, and the quality of the linkbetween the IAB-MT and the secondary IAB donor becomes better, theIAB-MT performs an IAB node group handover procedure.

In S261, that the primary donor node sends the handover request messageto the secondary donor node may be specifically: The primary donor CU ofthe primary donor node sends the handover request message to thesecondary donor CU of the secondary donor node, where the handoverrequest message may be an existing handover request message, or may be anewly defined IAB group handover request message, and the handoverrequest message carries the identifier of the first IAB node group (forexample, a group ID). In the secondary station addition process in S270,the primary IAB donor has sent contexts of the first IAB node and thechild node of the first IAB node to the secondary IAB donor. Therefore,the handover request message in S271 needs to carry only the identifierof the first IAB node group, and the primary IAB donor can find contextinformation of all members in the first IAB node group based on theidentifier of the first IAB node group.

In S262, that the secondary donor node sends the handover responsemessage to the primary donor node may be specifically: The secondary IABdonor sends the handover response message to the primary IAB donor,where the handover response message may be an existing handover responsemessage, or may be a newly defined IAB group handover response message.The handover response message is used to indicate the first IAB node tobe handed over to the secondary donor node, that is, indicate the IAB-MTto be handed over to the secondary donor CU.

Optionally, the handover response message carries at least one of thefollowing information:

-   -   at least one of handover command information instructing the        IAB-MT to execute handover or configuration information of the        child node of the first IAB node. The handover command        information is used to set up an air interface DRB between the        IAB-MT and the secondary IAB donor. For example, when the child        node of the first IAB node is UE, the configuration information        of the child node of the first IAB node may include an        association relationship between a UE PDCP and a DRB ID, and the        like.

After the primary donor CU sends the handover command information to thefirst IAB node, the IAB-MT of the first IAB node is handed over to thesecondary IAB donor, and removes a connection to the primary IAB donor.In this case, the secondary donor CU is used as a unique donor nodeconnected to the IAB-MT, and then the first IAB node may perform data orsignaling transmission with the secondary IAB donor.

In a process of donor node handover, the primary donor CU notifies, inthe handover request message, the secondary donor CU of only a groupidentifier of an IAB node that needs to be handed over, and does notneed to notify the secondary donor CU of context information of the IABnode and the child node of the IAB node, to reduce a handover processinglatency in a subsequent handover process and improve handoverefficiency.

Optionally, the primary donor node may further send, to the first IABnode, an IP address, of the first IAB node, anchored at the first donornode and/or configuration information of a serving cell, of the firstIAB node, belonging to the first donor node. Specifically, the primarydonor CU of the primary donor node may send, to the IAB-DU of the firstIAB node, a new IP address, of the IAB-DU, anchored at the secondarydonor CU connected to the IAB-DU and/or the configuration information ofthe serving cell, of the IAB-DU, belonging to the donor CU.

This application further provides a method for reporting support of anIAB function. The method may be applied to an IAB communication network.The IAB communication network includes an IAB donor node, the IAB donornode includes a centralized unit CU and at least one distributed unitDU, and the CU includes a centralized unit-user plane CU-CP entity and aCU-UP entity. The CU and the DU may be deployed on different physicaldevices, or the CU-UP entity and the CU-CP entity may be deployed on asame physical device. An application scenario of the method may be shownin FIG. 14 . As shown in FIG. 14 , the IAB donor may use an architecturein which a control plane CP and a user plane UP are split. In otherwords, the IAB donor includes an IAB donor CU (or may be referred to asa donor CU) and an IAB donor DU (or may be referred to as a donor DU),and the donor CU and the donor DU may be deployed on different physicaldevices, or may be deployed on a same physical device. Further, thedonor CU may be divided into a CU-CP entity and at least one CU-UPentity. The CU-CP entity is a control plane entity, and is configured toprovide a signaling control function. The CU-UP entity is a user planeentity, and is configured to provide transmission of data of a terminaldevice. The CU-CP entity and the CU-UP entity are connected through anE1 interface, the CU-CP entity and the donor DU are connected through anF1-C interface, and the CU-UP entity and the donor DU are connectedthrough an F1-U interface. The CU-CP includes an RRC function and a PDCPcontrol plane function (for example, configured to process data on asignaling radio bearer). The CU-UP includes an SDAP function and a PDCPuser plane function (for example, configured to process data on a radiobearer of the user equipment).

FIG. 15 is a schematic flowchart of a method 300 for reporting supportof an IAB function according to an embodiment of this application. Asshown in FIG. 15 , the method 300 shown in FIG. 15 may include step S310and step S320. The following describes in detail the steps in the method300 with reference to FIG. 15 . The method 300 includes S310 and S320.

-   -   S310: A CU-UP entity of a donor node generates fifth indication        information, where the fifth indication information is used to        indicate that the CU-UP entity of the donor node supports an IAB        function or supports access of an IAB node.    -   S320: The CU-UP entity of the donor node sends the fifth        indication information to a CU-CP entity of the donor node.

Specifically, in a scenario in which a donor CU uses a CP-UP splitarchitecture, to be specific, the donor CU includes one CU-CP (or may bereferred to as a donor-CU-CP) entity and a plurality of CU-UP (or may bereferred to as a donor-CU-UP) entities, to help a donor DU performrouting and bearer mapping, the CU-UP entity of the donor node needs toattach a differentiated services code point (DSCP)/flow label to data ofa terminal device based on configuration of the CU-CP entity of thedonor node. That is, in an IAB scenario, the CU-UP entity of the donornode needs to perform an additional label attaching operation.Therefore, the CU-CP entity of the donor node needs to know whether theCU-UP entity of the donor node supports the function, so that the CU-UPentity that is of the donor node and that supports the function can beselected for the terminal device to perform data transmission. That theCU-UP entity of the donor node supports the IAB function, supportsaccess of the IAB node, or supports IAB may be understood as that theCU-UP entity of the donor node supports attaching the DSCP/flow label tothe data of the terminal device. For example, if the CU-UP entity of thedonor node supports attaching or can attach the DSCP/flow label to thedata of the terminal device, the CU-UP entity of the donor node supportsthe IAB function or supports access of the IAB node. Therefore, in S310,any one of a plurality of CU-UP entities may generate the fifthindication information or support IAB, where the fifth indicationinformation is used to indicate that the CU-UP entity of the donor nodesupports the IAB function or supports access of the IAB node. In S320,the CU-UP entity of the donor node sends the fifth indicationinformation to the CU-CP entity of the donor node. After receiving thefifth indication information, the CU-CP entity of the donor node maydetermine that the CU-UP entity of the donor node supports the IABfunction, supports access of the IAB node, or supports IAB. In this way,when selecting CU-UP entities of the donor node to perform datatransmission, the CU-CP entity of the donor node can accurately selectCU-UP entities that are of the donor node and that support IAB, and usethe CP-UP entities of the donor node to perform routing and bearermapping before sending data, so as to ensure normal user-planetransmission and ensure quality and efficiency of data transmission of aterminal device.

Optionally, in a possible implementation, the fifth indicationinformation performs indication based on each public land mobile network(PLMN). One PLMN may be understood as one operator. For example, ChinaMobile, China Unicorn, and China Telecom correspond to different PLMNs.The CU-UP entities of the donor node may be leased by differentoperators together, some of the operators configure that the CU-UPentity of the donor node leased by the operators supports the IABfunction, supports access of the IAB node, or supports IAB, and some ofthe operators configure that the CU-UP entity of the donor node leasedby the operators does not support the IAB function, does not supportaccess of the IAB node, or does not support IAB. Therefore, the fifthindication information may perform indication based on the PLMN.

Optionally, the fifth indication information is in one-to-onecorrespondence with a PLMN identity. For example, the CU-UP entity ofthe donor node sends a list, for example, a supported PLMN list(Supported PLMNs List), to the CU-CP entity of the donor node. FIG. 16shows an example of the Supported PLMNs List. As shown in FIG. 16 , thelist includes a plurality of items, and each item includes one PLMNidentity (for example, a PLMN Identity) and one piece of fifthindication information (for example, iab-support). For example, ifiab-support is set to true or 1, it indicates that a CU-UP that is ofthe donor node and that corresponds to the PLMN supports IAB. Ifiab-support is set to false or 0, it indicates that a CU-UP that is ofthe donor node and that corresponds to the PLMN does not support IAB.

It should be understood that, the foregoing example is merely used todescribe an example of content specifically included when the fifthindication information performs indication based on the PLMN, and shouldnot impose any limitation on a specific form of the fifth indicationinformation or content included in the fifth indication information.This is not limited herein in this application.

Optionally, in another possible implementation, the fifth indicationinformation may perform indication based on one CU-UP entity of thedonor node, to be specific, fifth indication information sent by oneCU-UP entity of the donor node is used to indicate that the CU-UP entityof the donor node supports the IAB function, supports access of the IABnode, or supports IAB.

Optionally, in some possible implementations of this application, FIG.17 is a schematic flowchart of a method for reporting support of an IABfunction in some other embodiments of this application. S320 in themethod 300 may include S321 based on the steps in the method shown inFIG. 15 .

-   -   S321: The CU-UP entity of the donor node sends an E1 interface        setup request to the CU-CP entity of the donor node, where the        E1 interface setup request includes the fifth indication        information, and an E1 interface is an interface between the        CU-UP entity of the donor node and the CU-CP entity of the donor        node.

For step S310 shown in FIG. 17 , refer to the foregoing relateddescriptions of S310. For brevity, details are not described hereinagain.

In an E1 interface setup process, the CU-UP entity of the donor node mayactively report information about a capability that the CU-UP entitysupports IAB. That is, E1 interface setup may be triggered by the CU-UPentity of the donor node. In S321, the CU-UP entity of the donor nodemay carry the fifth indication information in the E1 interface setuprequest (E1 Setup Request) message sent to the CU-CP entity of the donornode, and the fifth indication information is used to indicate that theCU-UP entity of the donor node supports the IAB function, supports IAB,or supports access of the IAB node. Optionally, the fifth indicationinformation may perform indication based on each PLMN, or may performindication based on one CU-UP entity of the donor node. The CU-UP entityof the donor node actively triggers E1 interface setup, and carries, inthe E1 interface setup request message, indication informationindicating that the CU-UP entity of the donor node supports the IABfunction, supports access of the IAB node, or supports IAB, to help theCU-CP entity of the donor node select an appropriate CU-UP entity of thedonor node, and improve resource utilization.

Optionally, in some other possible implementations of this application,FIG. 18 is a schematic flowchart of a method for reporting support of anIAB function in some other embodiments of this application. The method300 may further include S322 based on the steps in the method shown inFIG. 15 .

-   -   S319: The CU-CP entity of the donor node sends an E1 interface        setup request message to the CU-UP entity of the donor node,        where an E1 interface is an interface between the CU-UP entity        of the donor node and the CU-CP entity of the donor node.    -   S320 in the method 300 may include S322.    -   S322: The CU-UP entity of the donor node sends an E1 interface        setup response message to the CU-CP entity of the donor node,        where the E1 interface setup response message includes the fifth        indication information.

For step S310 shown in FIG. 18 , refer to the foregoing relateddescriptions of S310. For brevity, details are not described hereinagain.

Not only the CU-UP entity of the donor node can actively trigger E1interface setup, but also the CU-CP entity of the donor node canactively trigger E1 interface setup. In S319, the CU-CP entity of thedonor node may send the E1 interface setup request (E1 Setup Request)message to the CU-UP entity of the donor node, to request to set up theE1 interface between the CU-UP entity of the donor node and the CU-CPentity of the donor node. Optionally, the E1 interface setup requestmessage may carry one piece of indication information. The indicationinformation is used to indicate the CU-UP entity of the donor node toreport a capability that the CU-UP entity of the donor node supports theIAB function, supports access of the IAB node, or supports IAB. Afterthe CU-UP entity of the donor node receives the E1 interface setuprequest message, in S322, the CU-UP entity of the donor node sends theE1 interface setup response (E1 Setup Response) message to the CU-CPentity of the donor node, where the E1 interface setup response messageincludes the fifth indication information. Optionally, the fifthindication information may perform indication based on each PLMN, or mayperform indication based on one CU-UP entity of the donor node. TheCU-CP entity of the donor node actively triggers E1 interface setup, andsends the E1 interface setup request message to the CU-UP entity of thedonor node. The CU-UP entity of the donor node carries, in the fed backE1 interface setup response message, indication information indicatingthat the CU-UP entity of the donor node supports the IAB function,supports access of the IAB node, or supports IAB, to help the CU-CPentity of the donor node select an appropriate CU-UP entity of the donornode, and improve resource utilization.

Optionally, in some other possible implementations of this application,FIG. 19 is a schematic flowchart of a method for reporting support of anIAB function in some other embodiments of this application. The method300 may further include S309 based on the steps in the method shown inFIG. 15 .

-   -   S309: The CU-CP entity of the donor node sends sixth indication        information to the CU-UP entity of the donor node, where the        sixth indication information is used to indicate the CU-UP        entity of the donor node to report a capability that the CU-UP        entity of the donor node supports the IAB function or supports        access of the IAB node.

For steps S310 and S320 shown in FIG. 19 , refer to the foregoingrelated descriptions of S310 and S320. For brevity, details are notdescribed herein again.

Before S310, that is, in S309, the CU-CP entity of the donor node maysend the sixth indication information to the CU-UP entity of the donornode, where the sixth indication information is used to indicate theCU-UP entity of the donor node to report the capability that the CU-UPentity of the donor node supports the IAB function, supports access ofthe IAB node, or supports IAB. That is, the CU-CP entity of the donornode may indicate the CU-UP entity of the donor node to report thecapability that the CU-UP entity of the donor node supports the IABfunction, supports access of the IAB node, or supports IAB. Afterreceiving the sixth indication information, the CU-UP entity of thedonor node determines that the CU-UP entity of the donor node needs toreport the capability of supporting the IAB function, supporting accessof the IAB node, or supporting IAB, so that S310 and S320 can beperformed.

Optionally, the sixth indication information may be an E1 interfacesetup request message.

This application further provides a method for adding a secondarystation by an IAB node. The method 400 may be applied to the applicationscenario shown in FIG. 6 . FIG. 20 is a schematic flowchart of a methodfor adding a secondary station by an IAB node according to an embodimentof this application. As shown in FIG. 20 , the method 400 shown in FIG.20 may include step S410 and step S420. The following describes indetail the steps in the method 400 with reference to FIG. 20 .

S410: A primary donor node sends a secondary station addition requestmessage to a first donor node, where the secondary station additionrequest message is used to request to add the first donor node as asecondary donor node of a first IAB node, and the primary donor node isa primary donor node of the first IAB node. The secondary stationaddition request message includes at least one of indication informationindicating that the first IAB node is a mobile IAB node, an identifierof a first IAB node group, member information of the first IAB nodegroup, or topology information of the first IAB node group, where thefirst IAB node group is a group including the first IAB node and a childnode of the first IAB node. Correspondingly, the first donor nodereceives the secondary station addition request message.

S420: The first donor node sends a secondary station addition responsemessage to the primary donor node, where the secondary station additionresponse message includes at least one of an IP address, of the firstIAB node, anchored at the first donor node or an IP address of the firstdonor node.

S430: The primary donor node sends seventh indication information to thefirst IAB node, where the seventh indication information is used toindicate the first IAB node to add the first donor node as a secondarydonor node (or secondary station).

Specifically, the first donor node may be a first IAB donor, and thefirst IAB donor may include a donor CU and a donor DU. The first IABdonor is equivalent to the secondary donor node in the method 200. Thefirst IAB node may be a mobile IAB node, and the first IAB node has setup a connection to the primary donor node (or referred to as a sourcedonor node) of the first IAB node and performs data transmission. Thefirst IAB node may include an IAB-MT and an IAB-DU, and the primarydonor node may include a primary donor CU and a primary donor DU. Inaddition, the IAB-MT of the first IAB node has been connected to theprimary donor CU, the IAB-DU of the first IAB node has set up an F1interface with the primary donor CU, and corresponding GTP tunnels havebeen set up, for different bearers of the child node of the first IABnode, between the IAB-DU and the primary donor CU.

To support IAB node group handover and reduce a service interruptionlatency caused by the handover, a dual connectivity procedure may beintroduced before the IAB-MT of the first IAB node is handed over to adonor IAB donor, and a user plane backhaul link between the IAB-MT andthe first IAB donor is set up in advance (where the backhaul link isused to transmit a service of the child node of an IAB node).

The first donor node in the method 400 is equivalent to the secondarydonor node in the method 200. For specific descriptions of S410, S420,and S430, refer to related specific descriptions of S260 in the method200. For brevity, details are not described herein again.

According to the method for adding a secondary station by an IAB nodeprovided in this application, a dual connectivity procedure isintroduced before IAB node handover. In a process in which an IAB nodeadds a secondary station, a primary IAB donor sends information about anIAB node group to a first IAB donor, and sets up a user plane backhaullink between the IAB node and the first IAB donor. When donor nodehandover is performed subsequently, only an identifier of the IAB nodegroup needs to be notified to the first donor node in a handoverrequest, to reduce a handover processing latency in a subsequenthandover process.

Optionally, the member information of the first IAB node group includes:

-   -   at least one of an identifier of the child node of the first IAB        node, quality of service QoS information of a service of the        child node of the first IAB node, or QoS corresponding to a        backhaul radio link control channel of the first IAB node under        a topology of the primary donor node.

Optionally, in a possible implementation, the method 400 furtherincludes the following steps.

-   -   S440: The primary donor node sends a handover request message to        the first donor node, where the handover request message        includes the identifier of the first IAB node group.    -   S450: The primary donor node receives a handover response        message from the first donor node, where the handover response        message is used to indicate the first IAB node to be handed over        to the first donor node.

For specific descriptions of S440 and S450, refer to related specificdescriptions of S271 and S272 in the method 200. For brevity, detailsare not described herein again.

Optionally, in a possible implementation, the method 400 furtherincludes: The primary donor node sends, to the first IAB node, the IPaddress, of the first IAB node, anchored at the first donor node and/orconfiguration information of a serving cell, of the first IAB node,belonging to the first donor node. Specifically, the primary donor CU ofthe primary donor node may send, to the IAB-DU of the first IAB node, anew IP address, of the IAB-DU, anchored at the secondary donor CUconnected to the IAB-DU and/or the configuration information of theserving cell, of the IAB-DU, belonging to the donor CU.

It should be understood that, for a specific process of the method 400and the implementations of the method 400, refer to related descriptionsof the method 200. For brevity, details are not described herein again.

According to the method for adding a secondary station by an IAB nodeprovided in this application, it is considered that a dual connectivityprocedure is introduced before an IAB-MT of an IAB node is handed overto a donor node, and a user plane backhaul link between the IAB-MT and afirst IAB donor (or a secondary IAB donor) is set up in advance. Whenquality of a link between the IAB-MT and a primary IAB donor becomesworse and quality of a link between the IAB-MT and the first IAB donorbecomes better, a handover procedure is performed, the IAB-MT is handedover to the first IAB donor, and removes the link between the IAB-MT andthe primary IAB donor, to reduce a service interruption latency in thehandover process.

This application further provides a method for obtaining an IP addressof an IAB node. The method may be applied a scenario in which if a donorDU to which an IAB node is attached or connected changes, for example,as shown in FIG. 6 , handover from the primary donor DU to the secondarydonor DU, the IAB node needs to re-obtain more IP addresses.Alternatively, the method may be further applied to a scenario in whichan IAB node determines, based on implementation of the IAB node, torequest more IP addresses (request more IP addresses based on anupper-layer service requirement of the IAB node) or a scenario in whichthe IAB node needs to obtain more IP addresses during or after an RRCre-setup or handover process, or in an initial access process of the IABnode.

FIG. 21 is a schematic flowchart of a method 500 for obtaining an IPaddress of an IAB node according to an embodiment of this application.The method 500 further includes S510 and S520.

-   -   S510: A first IAB node sends first information to a donor node        of the first IAB node, where the first information is used to        request to allocate one or more IP addresses to the first IAB        node.    -   S520: The donor node sends second information to the first IAB        node, where the second information includes the one or more IP        addresses allocated to the first IAB node, one or more IP        address prefixes allocated to the first IAB node, or first n        bits of the IP address allocated to the first IAB node, where n        is an integer greater than 0.

Specifically, the first IAB node may be a mobile IAB node or an IAB nodethat does not move. The first IAB node may be in dual connectivity, tobe specific, the first IAB node is connected to both two donor nodes, orthe first IAB node may be connected only to one donor node. The firstIAB node may include an IAB-MT and an IAB-DU. The donor node is a donornode currently connected to the first IAB node. For example, the donornode may be a primary donor node of the first IAB node, or a secondarydonor node of the first IAB node. The donor node may include a donor CUand a donor DU.

In S510, that a first IAB node sends first information to a donor nodeof the first IAB node may be specifically: The first IAB node sends thefirst information to the donor CU of the donor node. Correspondingly,the donor CU receives the first information.

In S520, after the donor CU receives the first information, the donor CUmay allocate one or more IP addresses to the first IAB node, or thedonor CU may request another node to allocate one or more IP addressesto the first IAB node, where the another node may be a donor DU, an OAMserver, a DHCP server, or the like. After allocating one or more IPaddresses to the first IAB node, the nodes may send the allocated one ormore IP addresses to the donor CU. The donor CU may send secondinformation to the first IAB node, where the second information includesthe one or more IP addresses allocated by the donor CU or the one ormore IP addresses allocated by the another node to the first IAB node.

Optionally, the second information may include at least one of the oneor more IP addresses allocated to the first IAB node, the one or more IPaddress prefixes allocated to the first IAB node, or first n bits of theone or more IP address allocated to the first IAB node, where n is aninteger greater than 0.

For specific descriptions of S510 and S520, refer to the descriptions ofS250 and S251 in the method 200. For brevity, details are not describedherein again.

According to the method for obtaining an IP address of an IAB nodeprovided in this application, when an IAB node needs to obtain more IPaddresses, the IAB node may request a donor CU to which the IAB node isattached to allocate more IP addresses to the IAB node, to satisfy arequirement of communication between the IAB node and new donor nodes(for example, the donor CU and a donor DU). This can ensure normalcommunication between the IAB node and a target donor node, and ensurecommunication efficiency.

Optionally, in a specific implementation, the first information includesat least one of a quantity of IP addresses requested to be allocated tothe first IAB node, a length of the one or more IP address prefixesrequested to be allocated to the first IAB node, or a value of n offirst n bits of the IP address requested to be allocated to the firstIAB node.

Optionally, in a specific implementation, the donor CU may be furtherdivided into a CU-CP entity and at least one CU-UP entity. The CU-UPentity and the CU-CP entity may be on different physical devices or on aunified physical device. The first information may further include atleast one of a quantity of IP addresses requested to be allocated to anF1-C interface, a length of the one or more IP address prefixesrequested to be allocated to the F1-C interface, a value of x of first xbits of the IP address requested to be allocated to the F1-C interface,a quantity of IP addresses requested to be allocated to an F1-Uinterface, a length of the one or more IP address prefixes requested tobe allocated to the F1-U interface, or a value of y of first y bits ofthe IP address requested to be allocated to the F1-U interface. The F1-Cinterface is a communication interface between the first IAB node andthe CU-CP entity, and the F1-U interface is a communication interfacebetween the first IAB node and the CU-UP entity. Both x and y areintegers greater than 0. For example, if the first information includesthe first n bits of the IP address requested to be allocated to thefirst IAB node, the quantity of IP addresses requested to be allocatedto the first IAB node=2^((total quantity of bits of the IP address-n)).If the first information further includes the first x bits of the IPaddress requested to be allocated to the F1-C interface, the quantity ofIP addresses requested to be allocated to the F1-Cinterface=2^((total quantity of bits of the IP address-x)). Similarly,if the quantity of IP addresses requested to be allocated to the F1-Uinterface=2^((total quantity of bits of the IP address-y)),2^((total quantity of bits of the IP address-n))=2^((total quantity of bits of the IP address-x))+2^((total quantity of bits of the IP address-y)).

It should be understood that, the quantity of IP addresses requested tobe allocated to the F1-C interface/the length of the one or more IPaddress prefixes requested to be allocated to the F1-C interface/thevalue of x of the first x bits of the IP address requested to beallocated to the F1-C interface specifically refers to a quantity of IPaddresses requested to be allocated to the first IAB node on the F1-Cinterface/a length of the one or more IP address prefixes requested tobe allocated to the first IAB node on the F1-C interface/a value of x offirst x bits of the IP address requested to be allocated to the firstIAB node on the F1-C interface. Similarly, the quantity of IP addressesrequested to be allocated to the F1-U interface/the length of the one ormore IP address prefixes requested to be allocated to the F1-Uinterface/the value of y of the first y bits of the IP address requestedto be allocated to the F1-U interface specifically refers to a quantityof IP addresses requested to be allocated to the first IAB node on theF1-U interface/a length of the one or more IP address prefixes requestedto be allocated to the first IAB node on the F1-U interface/a value of yof first y bits of the IP address requested to be allocated to the firstIAB node on the F1-U interface.

Optionally, in a specific implementation, the method 500 furtherincludes:

The donor node sends third indication information to the first IAB node,where the third indication information is used to indicate at least oneof a first IP address used for the F1-U interface in the one or more IPaddresses allocated to the first IAB node, a first IP address prefixused for the F1-U interface in the one or more IP address prefixesallocated to the first IAB node, first y bits of the first IP addressused for the F1-U interface, a second IP address used for the F1-Cinterface in the one or more IP addresses allocated to the first IABnode, a second IP address prefix used for the F1-C interface in the oneor more IP address prefixes allocated to the first IAB node, or first xbits of the second IP address used for the F1-C interface.

Optionally, in a specific implementation, because the donor node may befurther divided into a donor CU and at least one donor DU, the method500 further includes: The donor CU sends fourth indication informationto the first IAB node, where the fourth indication information is usedto indicate information that is about the donor DU and that correspondsto the one or more IP addresses allocated to the first IAB node. Theinformation about the donor DU may be an identifier of the donor DU, aname of the donor DU, an address of a BAP of the donor DU, an IP addressof the donor DU, or the like.

Optionally, in a specific implementation, because the donor node may befurther divided into a donor CU and a donor DU, when the donor DUallocates an IP address to the first IAB node, the method 500 furtherincludes: The donor CU forward, to the donor DU, the first informationsent by the first IAB node, and the donor DU allocates the one or moreIP addresses to the first IAB node. The donor DU may send the allocatedone or more IP addresses to the donor CU, and the donor CU notifies thefirst IAB node of the allocated one or more IP addresses. Optionally,the donor DU may notify the donor CU of at least one of the one or moreIP addresses allocated to the first IAB node, the one or more IP addressprefixes allocated to the first IAB node, or the first n bits of the IPaddress allocated to the first IAB node. Optionally, the donor DU mayfurther send third indication information to the donor CU.

In a possible implementation, the donor CU sends second information tothe first IAB node, where the second information includes the one ormore IP addresses allocated to the first IAB node. After receiving theone or more allocated IP addresses, the first IAB node determines IPaddresses used for F1-C interface communication and/or IP addresses usedfor F1-U interface communication.

In another possible implementation, if an OAM server allocates IPaddresses to the first IAB node, the OAM server may further indicate IPaddresses used for F1-U interface communication and/or IP addresses usedfor F1-C interface communication in a plurality of IP addressesallocated to the first IAB node.

It should be understood that, for a specific process of the method 500and the implementations of the method 500, refer to related descriptionsof the method 200. For brevity, details are not described herein again.

The foregoing describes in detail the method side embodiments providedin embodiments of this application with reference to FIG. 1 to FIG. 21 .The following describes in detail apparatus embodiments of thisapplication with reference to FIG. 22 to FIG. 28 . It should beunderstood that, descriptions of the method embodiments correspond todescriptions of the apparatus embodiments. Therefore, for a part notdescribed in detail, refer to the foregoing method embodiments.

FIG. 22 is a schematic diagram of a structure of a communicationapparatus 600 according to an embodiment of this application. Theapparatus 600 may correspond to the first IAB node or correspond to a DUof the first IAB node described in the method 200, the method 400, andthe method 500. Alternatively, the apparatus 600 may be a chip or acomponent used in the first IAB node, or may be a chip or a componentused in the DU of the first IAB node. In addition, modules or units inthe apparatus 600 are separately configured to perform actions orprocessing processes performed by the first IAB node or the DU of thefirst IAB node in the foregoing method embodiments.

As shown in FIG. 22 , the apparatus 600 may include a processing unit610 and a transceiver unit 620. The transceiver unit 620 is configuredto perform specific signal receiving and sending under driving of theprocessing unit 610.

In some possible implementations,

the processing unit 610 is configured to set up a first F1 interfacewith a primary donor node of the communication apparatus.

The processing unit 610 is further configured to obtain an internetprotocol IP address, of the communication apparatus, anchored at asecondary donor node connected to the communication apparatus and/orconfiguration information of a serving cell, of the communicationapparatus, belonging to the secondary donor node connected to thecommunication apparatus.

The transceiver unit 620 is configured to send, to the secondary donornode, a request for setting up a second F1 interface with the secondarydonor node, where the request includes the configuration information ofthe serving cell.

According to the communication apparatus provided in this application,the communication apparatus (for example, an IAB node) sets up an F1interface with a primary donor CU and a secondary donor CU. Before thecommunication apparatus is handed over from the primary donor CU to thesecondary donor CU, because the communication apparatus has set up theF1 interface with the secondary donor CU in advance, after thecommunication apparatus is handed over to the secondary donor CU, F1interface setup may not be triggered again. In this way, a latency forsetting up an F1 interface between an IAB-DU and the secondary donor CUafter the communication apparatus is handed over to the secondary donorCU is reduced, and a problem of service interruption caused by a latencyexisting when the communication apparatus is handed over to a donor nodeis avoided, thereby ensuring communication quality and improvingcommunication efficiency.

Optionally, in some embodiments of this application, the transceiverunit 620 is further configured to send first indication information tothe secondary donor node, where the first indication information is usedto indicate, to the secondary donor node, whether to start an operationof activating the serving cell of the communication apparatus.

Optionally, in some embodiments of this application, the transceiverunit 620 is further configured to send second indication information tothe secondary donor node, where the second indication informationincludes an identifier of the serving cell that the communicationapparatus requests the secondary donor node to activate.

Optionally, in some embodiments of this application, the transceiverunit 620 is further configured to send first information to thesecondary donor node, where the first information is used to request toallocate an IP address to the communication apparatus.

The transceiver unit 620 is further configured to receive secondinformation from the secondary donor node, where the second informationincludes at least one of an IP address allocated to the communicationapparatus, an IP address prefix allocated to the communicationapparatus, or first n bits of the IP address allocated to thecommunication apparatus, where n is an integer greater than 0.

Optionally, in some embodiments of this application, the firstinformation includes at least one of a quantity of IP addressesrequested to be allocated to the first IAB node, a length of the one ormore IP address prefixes requested to be allocated to the first IABnode, or a value of n of first n bits of the IP address requested to beallocated to the first IAB node.

Optionally, in some embodiments of this application, a centralized unitCU of the secondary donor node includes a centralized unit-control planeCU-CP entity and a centralized unit-user plane CU-UP entity. The firstinformation further includes at least one of a quantity of IP addressesrequested to be allocated to an F1-C interface, a length of the one ormore IP address prefixes requested to be allocated to the F1-Cinterface, a value of x of first x bits of the IP address requested tobe allocated to the F1-C interface, a quantity of IP addresses requestedto be allocated to an F1-U interface, a length of the one or more IPaddress prefixes requested to be allocated to the F1-U interface, or avalue of y of first y bits of the IP address requested to be allocatedto the F1-U interface, where the F1-C interface is a communicationinterface between the communication apparatus and the CU-CP entity ofthe secondary donor node, the F1-U interface is a communicationinterface between the communication apparatus and the CU-UP entity ofthe secondary donor node, and both x and y are integers greater than 0.

Optionally, in some implementations of this application, the transceiverunit 620 is further configured to receive third indication informationfrom the secondary donor node, where the third indication information isused to indicate at least one of a first IP address used for the F1-Uinterface in the one or more IP addresses allocated to the communicationapparatus, a length of the first IP address prefix used for the F1-Uinterface, first y bits of the first IP address used for the F1-Uinterface, a second IP address used for the F1-C interface in the one ormore IP addresses allocated to the communication apparatus, a length ofthe second IP address prefix used for the F1-C interface, or first xbits of the second IP address used for the F1-C interface.

Optionally, in some embodiments of this application, the secondary donornode includes a centralized unit CU and at least one distributed unitDU. The transceiver unit 620 is further configured to receive fourthindication information from the secondary donor node, where the fourthindication information is used to indicate information that is about theDU of the secondary donor node and that corresponds to the IP addressallocated to the communication apparatus.

Further, the apparatus 600 may further include a storage unit, and thetransceiver unit 620 may be a transceiver, an input/output interface, oran interface circuit. The storage unit is configured to storeinstructions executed by the transceiver unit 620 and the processingunit 610. The transceiver unit 620, the processing unit 610, and thestorage unit are coupled to each other. The storage unit storesinstructions. The processing unit 610 is configured to execute theinstructions stored in the storage unit. The transceiver unit 620 isconfigured to perform specific signal receiving and sending underdriving of the processing unit 610.

It should be understood that, for a specific process of performing theforegoing corresponding steps by the units in the apparatus 600, referto the foregoing related descriptions of the first IAB node or theIAB-DU in related embodiments in the method 200, the method 400, themethod 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 . For brevity,details are not described herein again.

Optionally, the transceiver unit 620 may include a receiving unit(module) and a sending unit (module), and may be configured to performthe steps of receiving information and sending information by the firstIAB node or the IAB-DU in related embodiments in the method 200, themethod 400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 .

It should be understood that, the transceiver unit 620 may be atransceiver, an input/output interface, or an interface circuit. Thestorage unit may be a memory. The processing unit 610 may be implementedby a processor. As shown in FIG. 23 , the communication apparatus 700may include a processor 710, a memory 720, and a transceiver 730.

The communication apparatus 600 shown in FIG. 22 or the communicationapparatus 700 shown in FIG. 23 can implement the steps performed by thefirst IAB node or the IAB-DU in related embodiments in the method 200,the method 400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG.21 . For similar descriptions, refer to the descriptions in theforegoing corresponding methods. To avoid repetition, details are notdescribed herein again.

It should be further understood that the communication apparatus 600shown in FIG. 22 or the communication apparatus 700 shown in FIG. 23 maybe the IAB node or the IAB-DU.

FIG. 24 is a schematic diagram of a structure of a communicationapparatus 800 according to an embodiment of this application. Theapparatus 800 may correspond to the secondary donor node or thesecondary donor CU in related embodiments in the method 200, the method400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 .Alternatively, the apparatus 800 may correspond to the primary donornode or the primary donor CU in related embodiments in the method 200,the method 400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG.21 . In addition, the modules or units in the apparatus 800 arerespectively configured to perform actions or processing processesperformed by the secondary donor node, the secondary donor CU, theprimary donor node, or the primary donor CU in the foregoing methodembodiments.

As shown in FIG. 24 , the apparatus 800 may include a transceiver unit810 and a processing unit 820. The transceiver unit 810 is configured toperform specific signal receiving and sending under driving of theprocessing unit 820.

In some possible implementations, when the apparatus 800 corresponds tothe secondary donor node or the secondary donor CU in relatedembodiments in the method 200, the method 400, the method 500, FIG. 7 toFIG. 13 , FIG. 20 , and FIG. 21 ,

the transceiver unit 810 is configured to receive, from a first IABnode, a request for setting up a second F1 interface with thecommunication apparatus, where the communication apparatus is asecondary donor node of the first IAB node.

The transceiver unit 810 is further configured to send, to the first IABnode, response information for setting up the second F1 interface, wherethe response information includes information about the communicationapparatus.

When the communication apparatus sets up the second F1 interface withthe first IAB node, the first IAB node maintains a first F1 interfacewith a primary donor node of the first IAB node.

According to the apparatus provided in this application, an IAB nodesets up an F1 interface with a primary donor CU and the communicationapparatus (a secondary donor CU). Before the IAB node is handed overfrom the primary donor CU to the communication apparatus, because theIAB node has set up the F1 interface with the communication apparatus inadvance, after the IAB node is handed over to the communicationapparatus, F1 interface setup may not be triggered again. In this way, alatency for setting up the F1 interface between the IAB-DU and thesecondary donor CU after the IAB node is handed over to a donor CU isreduced, and a problem of service interruption caused by a latencyexisting when the IAB node is handed over to a donor node is avoided,thereby ensuring communication quality and improving communicationefficiency.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to receive first indication informationfrom the first IAB node, where the first indication information is usedto indicate, to the communication apparatus, whether to start anoperation of activating a serving cell of the first IAB node.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to receive second indication informationfrom the first IAB node, where the second indication informationincludes an identifier of the serving cell that the first IAB noderequests the communication apparatus to activate.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to: receive first information from thefirst IAB node, where the first information is used to request toallocate an IP address to the first IAB node; and

send second information to the first IAB node, where the secondinformation includes at least one of an IP address allocated to thefirst IAB node, an IP address prefix allocated to the first IAB node, orfirst n bits of the IP address allocated to the first IAB node, where nis an integer greater than 0.

Optionally, in some embodiments of this application, the firstinformation includes at least one of a quantity of IP addressesrequested to be allocated to the first IAB node, a length of the one ormore IP address prefixes requested to be allocated to the first IABnode, or a value of n of first n bits of the IP address requested to beallocated to the first IAB node.

Optionally, in some embodiments of this application, a centralized unitCU of the communication apparatus includes a centralized unit-controlplane CU-CP entity and a centralized unit-user plane CU-UP entity. Thefirst information further includes at least one of a quantity of IPaddresses requested to be allocated to an F1-C interface, a length ofthe one or more IP address prefixes requested to be allocated to theF1-C interface, a value of x of first x bits of the IP address requestedto be allocated to the F1-C interface, a quantity of IP addressesrequested to be allocated to an F1-U interface, a length of the one ormore IP address prefixes requested to be allocated to the F1-Uinterface, or a value of y of first y bits of the IP address requestedto be allocated to the F1-U interface, where the F1-C interface is acommunication interface between the first IAB node and the CU-CP entityof the communication apparatus, the F1-U interface is a communicationinterface between the first IAB node and the CU-UP entity of thecommunication apparatus, and both x and y are integers greater than 0.

Optionally, in some implementations of this application, the transceiverunit 810 is further configured to send third indication information tothe first IAB node, where the third indication information is used toindicate at least one of a first IP address used for the F1-U interfacein the one or more IP addresses allocated to the first IAB node, alength of the first IP address prefix used for the F1-U interface, firsty bits of the first IP address used for the F1-U interface, a second IPaddress used for the F1-C interface in the one or more IP addressesallocated to the first IAB node, a length of the second IP addressprefix used for the F1-C interface, or first x bits of the second IPaddress used for the F1-C interface.

Optionally, in some embodiments of this application, the communicationapparatus includes a centralized unit CU and at least one distributedunit DU. The transceiver unit 810 is further configured to send fourthindication information to the first IAB node, where the fourthindication information is used to indicate information that is about theDU of the communication apparatus and that corresponds to the IP addressallocated to the first IAB node.

Optionally, in some embodiments of this application, the communicationapparatus includes a centralized unit CU and a distributed unit DU. Thetransceiver unit 810 is further configured to: send the firstinformation to the DU of the communication apparatus; and

-   -   receive, the DU of the communication apparatus, at least one of        the IP address allocated to the first IAB node, the IP address        prefix allocated to the first IAB node, or the first n bits of        the IP address allocated to the first IAB node.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to receive a secondary station additionrequest message from the primary donor node, where the secondary stationaddition request message is used to request to add the communicationapparatus as a secondary station of the first IAB node, and thesecondary station addition request message includes:

-   -   at least one of indication information used to indicate that the        first IAB node is a mobile IAB node, an identifier of a first        IAB node group, member information of the first IAB node group,        or topology information of the first IAB node group, where the        first IAB node group is a group including the first IAB node and        a child node of the first IAB node.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to send a secondary station additionresponse message to the primary donor node, where the secondary stationaddition response message includes:

-   -   at least one of an IP address, of the first IAB node, anchored        at the communication apparatus or an IP address of the        communication apparatus.

Optionally, in some embodiments of this application, the memberinformation of the first IAB node group includes:

-   -   at least one of an identifier of the child node of the first IAB        node, quality of service QoS information of a service of the        child node of the first IAB node, or QoS information        corresponding to a backhaul radio link control channel of the        first IAB node under a topology of the primary donor node.

In some other possible implementations, when the apparatus 800corresponds to the primary donor node or primary donor CU in relatedembodiments in the method 200, the method 400, the method 500, FIG. 7 toFIG. 13 , FIG. 20 , and FIG. 21 ,

-   -   the transceiver unit 810 is configured to send a secondary        station addition request message to a first donor node, where        the secondary station addition request message is used to        request to add the first donor node as a secondary donor node of        a first IAB node, and the communication apparatus is a primary        donor node of the first IAB node. The secondary station addition        request message includes at least one of indication information        indicating that the first IAB node is a mobile IAB node, an        identifier of a first IAB node group, member information of the        first IAB node group, or topology information of the first IAB        node group, where the first IAB node group is a group including        the first IAB node and a child node of the first IAB node.

The transceiver unit 810 is further configured to receive a secondarystation addition response message from the first donor node.

The transceiver unit 810 is further configured to send seventhindication information to the first IAB node, where the seventhindication information is used to indicate the first IAB node to add thefirst donor node as a secondary donor node.

According to the communication apparatus provided in this application, adual connectivity procedure is introduced before IAB node handover. In aprocess in which an IAB node adds a secondary station, the communicationapparatus sends information about an IAB node group to a first IABdonor, and sets up a user plane backhaul link between the IAB node andthe first IAB donor. When donor node handover is performed subsequently,only an identifier of the IAB node group needs to be notified to thefirst donor node in a handover request, to reduce a handover processinglatency in a subsequent handover process.

Optionally, in some embodiments of this application, the memberinformation of the first IAB node group includes:

at least one of an identifier of the child node of the first IAB node,quality of service QoS information of a service of the child node of thefirst IAB node, or QoS information corresponding to a backhaul radiolink control channel of the first IAB node under a topology of theprimary donor node.

The secondary station addition response message of the first donor nodeincludes at least one of an IP address, of the first IAB node, anchoredat the first donor node or an IP address of the first donor node.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to: send a handover request message tothe first donor node, where the handover request message includes theidentifier of the first IAB node group; and

receive a handover response message from the first donor node, where thehandover response message is used to indicate the first IAB node to behanded over to the first donor node.

Optionally, in some embodiments of this application, the transceiverunit 810 is further configured to send, to the first IAB node, an IPaddress, of the first IAB node, anchored at the first donor node and/orconfiguration information of a serving cell, of the first IAB node,belonging to the first donor node.

Further, the apparatus 800 may further include a storage unit, and thetransceiver unit 810 may be a transceiver, an input/output interface, oran interface circuit. The storage unit is configured to storeinstructions executed by the transceiver unit 810 and the processingunit 820. The transceiver unit 810, the processing unit 820, and thestorage unit are coupled to each other. The storage unit storesinstructions. The processing unit 820 is configured to execute theinstructions stored in the storage unit. The transceiver unit 810 isconfigured to perform specific signal receiving and sending underdriving of the processing unit 820.

It should be understood that, for a specific process of performing theforegoing corresponding steps by the units in the apparatus 800, referto the foregoing related descriptions of the secondary donor node, thesecondary donor CU, the primary donor node, or the primary donor CU inrelated embodiments in the method 200, the method 400, the method 500,FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 . For brevity, details are notdescribed herein again.

Optionally, the transceiver unit 810 may include a receiving unit(module) and a sending unit (module), and may be configured to performthe steps of receiving information and sending information by thesecondary donor node, the secondary donor CU, the primary donor node, orthe primary donor CU in related embodiments in the method 200, themethod 400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 .

It should be understood that, the transceiver unit 810 may be atransceiver, an input/output interface, or an interface circuit. Thestorage unit may be a memory. The processing unit 820 may be implementedby a processor. As shown in FIG. 25 , the communication apparatus 900may include a processor 910, a memory 920, and a transceiver 930.

The communication apparatus 800 shown in FIG. 24 or the communicationapparatus 900 shown in FIG. 25 can implement the steps performed by thesecondary donor node, the secondary donor CU, the primary donor node, orthe primary donor CU in related embodiments in the method 200, themethod 400, the method 500, FIG. 7 to FIG. 13 , FIG. 20 , and FIG. 21 .For similar descriptions, refer to the descriptions in the foregoingcorresponding methods. To avoid repetition, details are not describedherein again.

It should be further understood that the communication apparatus 800shown in FIG. 24 or the communication apparatus 900 shown in FIG. 25 maybe an IAB donor node.

FIG. 26 is a schematic diagram of a structure of a communicationapparatus 1000 according to an embodiment of this application. Theapparatus 100 may correspond to the CU-UP entity (node) of the donornode in related embodiments in the method 300, FIG. 15 , and FIG. 17 toFIG. 19 . The modules or units in the apparatus 1000 are separatelyconfigured to perform actions or processing processes performed by theCU-UP entity of the donor node in embodiments of the method 300.

As shown in FIG. 26 , the apparatus 1000 may include a processing unit1010 and a transceiver unit 1020. The transceiver unit 1020 isconfigured to perform specific signal receiving and sending underdriving of the processing unit 1010.

The processing unit 1010 is configured to generate fifth indicationinformation, where the fifth indication information is used to indicatethat the communication apparatus supports an IAB function or supportsaccess of an IAB node.

The transceiver unit 1020 is configured to send the fifth indicationinformation to a CU-CP entity of the donor node. The IAB donor nodeincludes a centralized unit CU and at least one distributed unit DU, theCU includes a centralized unit-control plane CU-CP entity and acentralized unit-user plane CU-UP entity, and the communicationapparatus is a CU-UP entity.

According to the communication apparatus provided in this application,in an IAB scenario, when selecting CU-UP entities of the donor node toperform data transmission, the CU-CP entity of the donor node canaccurately select CU-UP entities that are of the donor node and thatsupport IAB, and use the CP-UP entities of the donor node to performrouting and bearer mapping before sending data, so as to ensure normaluser-plane transmission and ensure quality and efficiency of datatransmission of a terminal device.

Optionally, in some embodiments of this application, the fifthindication information performs indication based on each public landmobile network PLMN.

Optionally, in some embodiments of this application, the transceiverunit 1020 is further configured to send an E1 interface setup request tothe CU-CP entity of the donor node, where the E1 interface setup requestincludes the fifth indication information, and the E1 interface is aninterface between the communication apparatus and the CU-CP entity ofthe donor node.

Optionally, in some embodiments of this application, the transceiverunit 1020 is further configured to: receive the E1 interface setuprequest from the CU-CP entity of the donor node, where the E1 interfaceis an interface between the communication apparatus and the CU-CP entityof the donor node; and

-   -   send an E1 interface setup response to the CU-CP entity of the        donor node, where the E1 interface setup response includes the        fifth indication information.

Optionally, in some embodiments of this application, the transceiverunit 1020 is further configured to receive sixth indication informationfrom the CU-CP entity of the donor node, where the sixth indicationinformation is used to indicate the communication apparatus to report acapability that the communication apparatus supports an IAB function orsupporting access of an IAB node.

Further, the apparatus 1000 may further include a storage unit, and thetransceiver unit 1020 may be a transceiver, an input/output interface,or an interface circuit. The storage unit is configured to storeinstructions executed by the transceiver unit 1020 and the processingunit 1010. The transceiver unit 1020, the processing unit 1010, and thestorage unit are coupled to each other. The storage unit storesinstructions. The processing unit 1010 is configured to execute theinstructions stored in the storage unit. The transceiver unit 1020 isconfigured to perform specific signal receiving and sending underdriving of the processing unit 1010.

It should be understood that, for a specific process of performing theforegoing corresponding steps by the units in the apparatus 1000, referto the foregoing related descriptions of the CU-UP entity (node) of thedonor node in related embodiments in the method 300, FIG. 15 , and FIG.17 to FIG. 19 . For brevity, details are not described herein again.

Optionally, the transceiver unit 1020 may include a receiving unit(module) and a sending unit (module), and may be configured to performthe steps of receiving information and sending information by the CU-UPentity (node) of the donor node in related embodiments in the method300, FIG. 15 , and FIG. 17 to FIG. 19 .

It should be understood that, the transceiver unit 1020 may be atransceiver, an input/output interface, or an interface circuit. Thestorage unit may be a memory. The processing unit 1010 may beimplemented by a processor. As shown in FIG. 27 , the communicationapparatus 1100 may include a processor 1110, a memory 1120, and atransceiver 1130.

The communication apparatus 1000 shown in FIG. 26 or the communicationapparatus 1100 shown in FIG. 27 can implement the steps performed by theCU-UP entity (node) of the donor node in related embodiments in themethod 300, FIG. 15 , and FIG. 17 to FIG. 19 . For similar descriptions,refer to the descriptions in the foregoing corresponding methods. Toavoid repetition, details are not described herein again.

It should be further understood that the communication apparatus 1000shown in FIG. 26 or the communication apparatus 1100 shown in FIG. 27may be the CU-UP entity (node) of the donor node.

It should be further understood that division of units in the apparatusis merely logical function division. During actual implementation, allor some of the units may be integrated into one physical entity or maybe physically separated. In addition, all the units in the apparatus maybe implemented in a form in which a processing element invokes software,or may be implemented in a form of hardware; or some units may beimplemented in a form in which a processing element invokes software,and some units are implemented in a form of hardware. For example, unitsmay be separately disposed processing elements, or may be integratedinto a chip of the apparatus for implementation. In addition, the unitsmay be stored in a memory in a program form, and is invoked by aprocessing element of the apparatus to perform functions of the units.The processing element herein may also be referred to as a processor,and may be an integrated circuit having a signal processing capability.In an implementation process, steps in the foregoing methods or theforegoing units may be implemented by using a hardware integrated logiccircuit in the processor element, or may be implemented in a form inwhich the processing element invokes software.

In an example, a unit in any one of the foregoing apparatuses may be oneor more integrated circuits configured to implement the foregoingmethod, for example, one or more application-specific integratedcircuits (ASICs), one or more digital signal processors (DSPs), one ormore field programmable gate arrays (FPGAs), or a combination of atleast two of these integrated circuit forms. For another example, whenthe units in the apparatus may be implemented in a form in which aprocessing element schedules a program, the processing element may be ageneral purpose processor, for example, a central processing unit (CPU)or another processor that can invoke the program. For another example,the units may be integrated together and implemented in a form of asystem-on-a-chip (SOC).

It should be understood that in embodiments of this application, theprocessor may be a central processing unit (CPU), or the processor maybe another general-purpose processor, a DSP, an ASIC, an FPGA, oranother programmable logic device, discrete gate or transistor logicdevice, discrete hardware component, or the like. The general-purposeprocessor may be a microprocessor, or the processor may be anyconventional processor or the like.

All or some of the foregoing embodiments may be implemented by software,hardware, firmware, or any combination thereof. When the software isused to implement the embodiments, all or some of the foregoingembodiments may be implemented in a form of a computer program product.The computer program product includes one or more computer instructionsor computer programs. When the program instructions or the computerprograms are loaded and executed on a computer, the procedures orfunctions according to the embodiments of this application are all orpartially generated. The computer may be a general-purpose computer, adedicated computer, a computer network, or another programmableapparatus.

The computer instructions may be stored in a computer-readable storagemedium or may be transmitted from one computer-readable storage mediumto another computer-readable storage medium. For example, the computerinstructions may be transmitted from a website, computer, server, ordata center to another website, computer, server, or data center in awired (for example, infrared, radio, or microwave) manner. Thecomputer-readable storage medium may be any usable medium accessible bya computer, or a data storage device, such as a server or a data center,integrating one or more usable media. The usable medium may be amagnetic medium (for example, a floppy disk, a hard disk, or a magnetictape), an optical medium (for example, a DVD), or a semiconductormedium. The semiconductor medium may be a solid-state drive.

FIG. 28 is a schematic diagram of a structure of an IAB node or an IABdonor node according to an embodiment of this application. The structureis configured to implement operations of the IAB node or the IAB donornode in the foregoing embodiments. As shown in FIG. 28 , the IAB node orthe IAB donor node includes an antenna 1201, a radio frequency apparatus1202, and a baseband apparatus 1203. The antenna 1201 is connected tothe radio frequency apparatus 1202. In an uplink direction, the radiofrequency apparatus 1202 receives, by using the antenna 1201,information sent by a terminal device, and sends, to the basebandapparatus 1203, the information sent by the terminal for processing. Ina downlink direction, the baseband apparatus 1203 processes informationabout the terminal, and sends the information about the terminal deviceto the radio frequency apparatus 1202. The radio frequency apparatus1202 processes the information about the terminal, and then sends theprocessed information about the terminal to the terminal by using theantenna 1201.

The baseband apparatus 1203 may include one or more processing elements12031, for example, include a main control CPU and another integratedcircuit. In addition, the baseband apparatus 1203 may further include astorage element 12032 and an interface 12033. The storage element 12032is configured to store a program and data. The interface 12033 isconfigured to exchange information with the radio frequency apparatus1202, and the interface is, for example, a common public radio interface(CPRI). The foregoing apparatus used for the network device may belocated in the baseband apparatus 1203. For example, the foregoingapparatus used for the network device may be a chip in the basebandapparatus 1203. The chip includes at least one processing element and aninterface circuit. The processing element is configured to perform thesteps of any method performed by the IAB node or the IAB donor node. Theinterface circuit is configured to communicate with another apparatus.In an implementation, units of the IAB node or the IAB donor node thatimplement the steps in the foregoing methods may be implemented by aprocessing element scheduling a program. For example, the apparatus usedfor the IAB node or the IAB donor node includes a processing element anda storage element. The processing element invokes a program stored inthe storage element, to perform the methods performed by the IAB node orthe IAB donor node in the foregoing method embodiments. The storageelement may be a storage element that is located on a same chip as theprocessing element, that is, an on-chip storage element, or may be astorage element that is located on a different chip from the processingelement, that is, an off-chip storage element.

In another implementation, units of the IAB node or the IAB donor nodethat implement the steps in the foregoing methods may be configured asone or more processing elements. The processing elements are disposed inthe baseband apparatus. The processing element herein may be anintegrated circuit, for example, one or more ASICs, one or more DSPs,one or more FPGAs, or a combination of the types of integrated circuits.The integrated circuits may be integrated together to form a chip.

Units of the IAB node or the IAB donor node that implement the steps inthe foregoing methods may be integrated together, and implemented in aform of a system-on-a-chip. For example, the baseband apparatus includesthe SOC chip, configured to implement the foregoing methods.

The IAB node or the IAB donor node in the foregoing apparatusembodiments may completely correspond to the IAB node or the IAB donornode in the method embodiments, and a corresponding module or unitperforms a corresponding step. For example, when the apparatus isimplemented in a chip manner, the receiving unit may be an interfacecircuit configured by the chip to receive a signal from another chip orapparatus. The foregoing unit configured for sending is an interfacecircuit of the apparatus, and is configured to send a signal to anotherapparatus. For example, when the apparatus is implemented in the mannerof the chip, the sending unit is an interface circuit that is of thechip and that is configured to send a signal from another chip orapparatus.

An embodiment of this application further provides a communicationsystem. The communication system includes the foregoing first IAB node,the foregoing secondary donor, and the foregoing primary donor node.

An embodiment of this application further provides a computer-readablemedium, configured to store computer program code. The computer programincludes instructions used to perform the method provided in embodimentsof this application in the method 200 to the method 500. The readablemedium may be a read-only memory (ROM) or a random access memory (RAM).This is not limited in this embodiment of this application.

This application further provides a computer program product. Thecomputer program product includes instructions. When the instructionsare executed, an IAB node, a secondary donor, and a primary donor nodeare enabled to separately perform operations of the IAB node, thesecondary donor, and the primary donor node that correspond to theforegoing method.

An embodiment of this application further provides a system chip. Thesystem chip includes a processing unit and a communication unit. Theprocessing unit may be, for example, a processor, and the communicationunit may be, for example, an input/output interface, a pin, a circuit,or the like. The processing unit may execute computer instructions, sothat a chip in the communication apparatus performs any method providedin the foregoing embodiments of this application.

Optionally, any communication apparatus provided in the foregoingembodiments of this application may include the system chip.

Optionally, the computer instructions are stored in a storage unit.

Optionally, the storage unit is a storage unit in the chip, for example,a register or a cache. The storage unit may further be a storage unit,such as a ROM, another type of static storage device that can storestatic information and instructions, or a RAM, that is outside the chipand that is in the terminal. The processor mentioned anywhere above maybe a CPU, a microprocessor, an ASIC, or one or more integrated circuitsfor controlling program execution of the foregoing of communicationmethod. The processing unit and the storage unit may be decoupled, areseparately disposed on different physical devices, and are connected ina wired or wireless manner to implement respective functions of theprocessing unit and the storage unit, so as to support the system chipin implementing various functions in the foregoing embodiments.Alternatively, the processing unit and the memory may be coupled to asame device.

It may be understood that, in embodiments of this application, thememory may be a volatile memory or a nonvolatile memory, or may includeboth a volatile memory and a nonvolatile memory. The nonvolatile memorymay be a read-only memory (ROM), a programmable read-only memory (PROM),an erasable programmable read-only memory (EPROM), an electricallyerasable programmable read-only memory (EEPROM), or a flash memory. Thevolatile memory may be a random access memory (RAM), used as an externalcache. By way of example but not limitative description, many forms ofrandom access memories (RAMs) may be used, for example, a static randomaccess memory (static RAM, SRAM), a dynamic random access memory(dynamic RAM, DRAM), a synchronous dynamic random access memory(synchronous DRAM, SDRAM), a double data rate-synchronous dynamic randomaccess memory (double Data Rate SDRAM, DDR SDRAM), an enhancedsynchronous dynamic random access memory (enhanced SDRAM, ESDRAM), asynchlink dynamic random access memory (synchlink DRAM, SLDRAM), and adirect rambus random access memory (direct rambus RAM, DR RAM).

The terms “system” and “network” in this specification may be usedinterchangeably in this specification. The term “and/or” in thisspecification describes only an association relationship for describingassociated objects and represents that three relationships may exist.For example, A and/or B may represent the following three cases: Only Aexists, both A and B exist, and only B exists. In addition, thecharacter “1” in this specification usually indicates an “or”relationship between the associated objects.

Terms “uplink” and “downlink” in this application are used to describe adata/information transmission direction in a specific scenario. Forexample, the “uplink” direction usually refers to a direction in whichdata/information is transmitted from a terminal to a network side, or adirection in which a distributed unit transmits data/information to acentralized unit, and the “downlink” direction usually refers to adirection in which data/information is transmitted from a network sideto a terminal. Alternatively, in a transmission direction from thecentralized unit to the distributed unit, it may be understood that“uplink” and “downlink” are merely used to describe a data/informationtransmission direction, and a specific start/end device of thedata/information transmission is not limited.

In this application, names may be assigned to various objects such asvarious messages/information/devices/networkelements/systems/apparatuses/actions/operations/procedures/concepts. Itmay be understood that these specific names do not constitute alimitation on related objects, the assigned names may change withfactors such as a scenario, a context, or a use habit. Technicalmeanings of technical terms in this application should be mainlyunderstood based on functions and technical effects reflected/executedby the technical terms in the technical solutions.

A person of ordinary skill in the art may be aware that units andalgorithm steps in the examples described with reference to theembodiments disclosed in this specification may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions of each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments. Details arenot described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the unit division is merelylogical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented through some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualrequirements to achieve the objectives of the solutions of theembodiments.

In addition, function units in the embodiments of this application maybe integrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit.

When the functions are implemented in a form of a software function unitand sold or used as an independent product, the functions may be storedin a computer-readable storage medium. Based on such an understanding,the technical solutions of this application essentially, or the partcontributing to the conventional technology, or some of the technicalsolutions may be implemented in a form of a software product. Thecomputer software product is stored in a storage medium, and includesseveral instructions for instructing a computer device (which may be apersonal computer, a server, or a network device) to perform all or someof the steps of the method described in embodiments of this application.The storage medium includes a USB flash drive, a removable hard disk, aread-only memory (ROM), and a random access memory.

The foregoing descriptions are merely specific implementations of thisapplication, but are not intended to limit the protection scope of thisapplication. Any variation or replacement readily figured out by aperson skilled in the art within the technical scope disclosed in thisapplication shall fall within the protection scope of this application.Therefore, the protection scope of this application shall be subject tothe protection scope of the claims.

What is claimed is:
 1. A communication apparatus, comprising: at leastone processor; and one or more memories coupled to the at least oneprocessor and storing programming instructions for execution by the atleast one processor to perform operations comprising: receiving firstinformation from an integrated access and backhaul (IAB) node, whereinthe first information is used to request to allocate internet protocol(IP) address to the IAB node, wherein the communication apparatus is acentralized unit (CU) of an IAB donor or an apparatus included in the CUof the IAB donor, and wherein the first information comprises a quantityof IP addresses requested to be allocated to the IAB node or a quantityof IP addresses requested to be allocated to an F1 control plane (F1-C)interface or an F1 user plane (F1-U) interface, wherein the F1-Cinterface is a communication interface between the IAB node and aCU-control plane (CU-CP) of the IAB donor, and the F1-U interface is acommunication interface between the IAB node and a CU-user plane (CU-UP)of the IAB donor; in response to receiving the first information,sending, to a distributed unit (DU) of the IAB donor, a request forallocating IP address to the IAB node; receiving, from the DU of the IABdonor, one or more IP addresses that are allocated to the IAB node; andsending, to the IAB node, a backhaul adaptation protocol (BAP) addressthat is of the DU of the IAB donor and that corresponds to the one ormore IP addresses.
 2. The apparatus according to claim 1, wherein theoperations comprise: sending indication information to the IAB node,wherein the indication information indicates an IP address used for anF1 user plane (F1-U) interface or an F1 control plane (F1-C) interfacein the one or more IP addresses.
 3. The apparatus according to claim 1,wherein the operations comprise: sending indication information to theIAB node, wherein the indication information indicates an IP addressprefix used for an F1 user plane (F1-U) interface or an F1 control plane(F1-C) interface in the one or more IP address prefixes.
 4. Acommunication apparatus, comprising: at least one processor; and one ormore memories coupled to the at least one processor and storingprogramming instructions for execution by the at least one processor toperform operations comprising: sending first information to acentralized unit (CU) of an integrated access and backhaul (IAB) donor,wherein the first information is used to request to allocate internetprotocol (IP) address to an IAB node, and wherein the communicationapparatus is the IAB node or an apparatus included in the IAB node, andwherein the first information comprises a quantity of IP addressesrequested to be allocated to the IAB node or a quantity of IP addressesrequested to be allocated to an F1 control plane (F1-C) interface or anF1 user plane (F1-U) interface, wherein the F1-C interface is acommunication interface between the IAB node and a CU-control plane(CU-CP) of the IAB donor, and the F1-U interface is a communicationinterface between the IAB node and a CU-user plane (CU-UP) of the IABdonor; and receiving a backhaul adaptation protocol (BAP) address fromthe CU of the IAB donor, wherein the BAP address is of a distributedunit (DU) of the IAB donor and the BAP address corresponds to one ormore IP addresses that are allocated to the IAB node.
 5. The apparatusaccording to claim 4, wherein the operations comprise: receivingindication information from the CU of the IAB donor, wherein theindication information indicates an IP address used for an F1 user plane(F1-U) interface or an F1 control plane (F1-C) interface in the one ormore IP addresses.
 6. The apparatus according to claim 4, wherein theoperations comprise: receiving indication information from the CU of theIAB donor, wherein the indication information indicates an IP addressprefix used for an F1 user plane (F1-U) interface or an F1 control plane(F1-C) interface in the one or more IP address prefixes.
 7. Theapparatus according to claim 4, wherein the one or more IP addresses areallocated by the DU of the IAB donor.
 8. The apparatus according toclaim 1, wherein the operations further comprise: sending the one ormore IP addresses to the IAB node.
 9. The apparatus according to claim4, wherein the operations further comprise: receiving the one or more IPaddress from the CU of the IAB donor.
 10. A communication system,comprising: a centralized unit (CU) of an integrated access and backhaul(IAB) donor, wherein the CU of the IAB donor comprises: at least onefirst processor; and one or more first memories coupled to the at leastone first processor and storing first programming instructions forexecution by the at least one first processor to perform firstoperations comprising: receiving first information from an IAB node,wherein the first information is used to request to allocate internetprotocol (IP) address to the IAB node, and wherein the first informationcomprises a quantity of IP addresses requested to be allocated to theIAB node or a quantity of IP addresses requested to be allocated to anF1 control plane (F1-C) interface or an F1 user plane (F1-U) interface,wherein the F1-C interface is a communication interface between the IABnode and a CU-control plane (CU-CP) of the IAB donor, and the F1-Uinterface is a communication interface between the IAB node and aCU-user plane (CU-UP) of the IAB donor; in response to receiving thefirst information, sending, to a distributed unit (DU) of the IAB donor,a request for allocating IP address to the IAB node; receiving, from theDU of the IAB donor, one or more IP addresses that are allocated to theIAB node; and sending, to the IAB node, a backhaul adaptation protocol(BAP) address that is of the DU of the IAB donor and that corresponds tothe one or more IP addresses; and the IAB node, wherein the IAB nodecomprises: at least one second processor; and one or more secondmemories coupled to the at least one second processor and storing secondprogramming instructions for execution by the at least one secondprocessor to perform second operations comprising: sending the firstinformation to the CU of the IAB donor; and receiving the BAP addressfrom the CU of the IAB donor.
 11. The communication system according toclaim 10, wherein the first operations comprise: sending indicationinformation to the IAB node, wherein the indication informationindicates an IP address used for an F1 user plane (F1-U) interface or anF1 control plane (F1-C) interface in the one or more IP addresses. 12.The communication system according to claim 10, wherein the firstoperations further comprise: sending the one or more IP addresses to theIAB node.